How much headache is it going to be to install Win 7

It is possible, you will lose updates tho. This link helped me out, figured id share. I was asked to do this for a customer once.

Best of Luck to you!

Http://community.spiceworks.com/topic/2016296-how-to-easily-get-around-the-windows-7-update-block-on-kaby-lake-and-ryzen-cpus

Its worth pointing out that extended support for Windows 7 is set to end in a little over a year, after which the OS won't even receive security updates.

Yes, this didn't really answer the question. : P I suspect it would be similar to the process for existing Coffee Lake processors, though I don't know exactly the details of what that entails.

if you want to try use a tool called 7lite to make a new windows 7 iso. try to slip stream the chipset drivers for windows 10 into it. on my dad pc i used classic shell. they stop updating it but it still on the net. makes windows 10 look and act like windows 7.

In truth, it's not that much different. Yes, some of the Control panel stuff has been moved.
But a window is a window is a window.

If you made the change from XP to Vista to 7...this isn't any more different.

Agreed with USAFRet.
I don't see what you have against upgrading to W10.
I've been using it since day 1 and although there were some bumps in the road for a little while as of right now it's a fantastic OS that works perfectly (at least for me) and I'm a power user.

However, if your gripes are with a few known things about W10 I can hopefully put your mind at ease a little bit with the following information.

In regards to privacy:
You have a couple of options when it comes to completely shutting out Microsoft from getting any info from your system about your habits but the easiest and best one is to use a free program called "Spybot Anti-Beacon".
You just install it then run it as administrator and click on everything to turn things off.
It's ok if a few things say they failed, it just means you don't have that particular program or service from Microsoft installed on the PC.

Alternatively, you can just look at it this way, it's not like your life and habits are a secret these days. If you happen to have a smart device of any kind (Apple or Android) and use social media apps like Facebook or the Chrome web browser (this goes for Chrome browser on PC even with W7 BTW) then your microphone is listening to you for keywords that can be related to advertisements that they can shove in your face and the websites you visit and whatnot is all logged. So it's not like what Microsoft is doing with W10 is any different.

In regards to the general look of the OS and the changing about of a few key UI elements, this can easily be remedied via a couple of 3rd party pieces of software.

If you just like the way the start menu looks on W7 vs W10 (btw, if you think the start menu is the same as W8/8.1 where it's a big start screen with big button icons then you're wrong, they went back to the start menu and added the tiles to it along side a programs list which you can just right click and unpin these tiles at your leisure) then using something like "Classic Shell" as was stated by the user smorizio above can bring it back to how it was.

In regards to the control panel. It's not replaced by the settings menu of W10, it's just hidden.... sort of.
You can open the start menu and start typing control panel and it will show up and you can just open it and pin it to the task bar for quick easy access (this is what I do).

If you like the aero look of W7 there are some heavy modification programs out there that can do the modding for you and make it theme like W7 but they are usually a pain to work with, buggy, and put quite a bit of load on your system resources to run that way.
As an alternative, there are is another option for aero that keeps the W10 window theme and just adds the aero effect to it which is to make it transparent with a blur effect on it.

In regards to backwards compatibility with programs and games, for the most part it is just as backwards compatible as W7 and when it comes to gaming, if you have a gripe about gamemode ruining game performance, then you clearly haven't been keeping up to date as Microsoft has completely fixed that issue and did so a while back and now games run just fine with it on, and in fact, if you disable it (which now has to be forcefully done through editing the registry) it can actually hurt the performance of your games. Works great now and should just be left alone. (I say this from personal experience.)

If your personal gripes about upgrading to W10 has to do with something else entirely, there may yet still be a solution to it so please feel free to share.

--UPDATE--

It took me a hot minute to write my post and now have seen your posts.

In regards to Windows Media Center is there a specific piece of hardware you use it with for your HTPC needs?

Chances are, Kodi will work wonders for you.
Or you can always find a "free" way of getting WMC on W10.

As for bloat ware, I've never had an issue. Most "bloatware" comes from preinstalled W10 on prebuilt computers you buy.
The other stuff that Microsoft themselves preloads on the system that comes from the Microsoft Store don't take up hardly any space and don't interfere with your usage of the system in the slightest.

I should also add that if you upgrade, you should download the Windows Media Creation Tool and have a flash drive with a capacity of at least 8GB and use the tool to create a bootable USB installation. (btw, this tool is provided free by Microsoft themselves and should be downloaded from their site)
Use once the bootable drive is created, just double click on it in My Computer to run it and choose to upgrade your PC. It should just transfer over your license from W7 and activate W10. Even though people say they stopped doing the "free" upgrade a long time ago for some reason this usually still works.
And if not you can do one of three things:

1. Contact Microsoft and hassle them politely about giving you a free upgrade activation. This usually works as they seem to be pretty generous most of the time about doing this.

2. If that doesn't work you can of course purchase an activation either directly from them or take a chance on a grey market key that costs less.

3. <Redacted by Moderator> against the forums rules since it relates to piracy, so don't ask.
<And don't suggest, even offhandedly>

I thought wmp is included already? Just not the European and Korean versions Win10 - N and Win10 - Kn excluded wmp, for senseless squabble. Normal Win10 should be fine afaik

Or is wm center different?

again, don't know how you use WMC, but if it's just through standard upnp/dlna type connectivity and playback then you can also just use homegroup which is built into windows. But if you are using that method of connectivity and want a more feature rich software that acts as a library for content as well then Kodi is best.

After doing some checking up on this, there is not WMC for W10 period. They don't want to support it. Looks like there's an unofficial community maintained version that's been forked from the original and modified to install and run on W10 and is for all intents and purposes straight up WMC from W7 as far as I can tell.

Alternatively though I really do recommend to just switch to Kodi and give it a shot. Will take a little bit of setup to get library sharing going but isn't difficult. No more difficult than getting WMC up and running properly.

But if you find it's too difficult/different and you just can't get used to it and don't like it, here's a tutorial guide for getting WMC on W10.
https://www.howtogeek.com/258695/how-to-install-windows-media-center-on-windows-10/