Yes you can on the H110M provided the BIOS is on the Kaby Lake support version, which version 3407 is if i'm not mistaken. I'd take a look on Asus's website just to be certain otherwise it will not post with a 7th Gen CPU.
You can indeed use the i3's stock fan since they are the same socket but you might as well just use the brand new one that will come with the retail edition of the i7-7700 unless you are buying it separate.
The performance/speed difference from i3-6100 to i7-7700 is quite a lot, it'll be especially noticeable when multi-tasking, doing intense workloads like Rendering and Editing, better performance in CPU intensive and most other modern games especially when streaming/recording. If you do any of these things you'll definitely notice the difference, typical desktop tasks like Internet browsing, Document reading/writing will be less noticeable. Hope this helps