Will I notice a difference between X370 x B350 x A320?

rocktalkrock said it pretty well but I would like to add a few things...

if you've truly no interest in overclocking then an A320 based board would probably do you well. But it can not overclock at all so if that itch should arise you can't scratch it.

b350 motherboards will overclock but, as rocktalkrock noted, they're the ones that are most limited with power delivery to the CPU so it won't overclock as far as a good X370...especially so with 8 core CPU's. .

The X370 chipset is the only one that will allow you to run Nvidia cards in SLI, if that's important to you.

X370 also has more PCIe lanes available so you're more likely to find more x8 or x4 slots expansion slots, more M.2 interfaces, more USB 3.1 gen 2 ports and/or more SATA III ports, for instance, on those boards.

Other than that: look for features you need and expansion you consider necessary.

The best advice if you aren't sure about your chipset....don't get an x370. Chances are this is your first AMD build or you are getting back into PC building. Don't get an A320 because you will be restricted on features as well as OC capabilities as you learn more about the board you select and it's features.. I have an X370 Asus board but run B350 MSI Tomahawk PLus' in two other Riggs at my home and couldn't be happier. The Plus model has more vrm's,, the Asmedia USB chipset for better handoff, and it looks awesome (heatsink,and LEDs on back are RGB not just red ).Many people criticise hardware quality (VRM,Components, etc) but they have been great and you can usually grab one brand new for $79 after the rebate on new egg. My B350 sets have been able to OC several Ryzen 5 1400 to 3.8/3.9 and it was stable and my RAM clocked to 3200 on the first post with no adjustments . Also I can use dual gpus on the b350 board even thou AMD states it's not supported for the chipset. X370 boards are really for your enthusiasts, more room to overclock and also have more vrm's which help with power distribution to your CPU, Dimms etc. So bottom line...if you have to ask go with the B350 unless you are planning on spending the extra cheddar for features you won't use or don't need. Good luck. Also look at the ASRock boards, they have stepped their game way up with the new chipsets. MSI IS NOT GARBAGE...WELL THE CHEAP BOARDS ARE. Good luck hope it helps.
Basic budeget PC:
Ryzen 5 1400 (3.6ghz)
16GB Corsair Vengence RGB DDR4 3000mhz (has better timings than the 3200)
B350 MSI Tomahawk Plus
Deepcool Earlkase
Coolermaster Liquidmaster lite 120 (cool trick is to pop the cap off the pump and you can use colored cellophane or non permanent ink to color the inside letters so it matches your color scheme)
Corsair,Seagate or Evga 550 PSU (don't spent money on a cheap PSU because it has more watts, a quality 550 is 10 times better than an 800w cheap no name)
Samsung m.2 SSD or 850 Evo with Seagate Barracuda HDD, don't skimp on your SSD, it truly matters
EVGA GeForce 1050 or 1060 is usually more than you need,GPU tricky, go with what suits your needs, don't spend $250 on a card because it's shiny, start on ebay (cards starting at $10 and GDDR5 2GB+ for $50)
This setup easily handles just about any game and if your smart you can build it for less than $500. Scores a 78 percentile for Mid to Upper class gaming PC thru several benches.