This is a praiseworthy endeavor, but you're wrongly focusing on hardware setup instead of the other things you talked about: software setup and exclusive gaming titles. Hardware setup is a cakewalk with PCs today. It's the software setup where PC gaming gets more laborious, but it's this potential for labor that creates all of the possibilities (like mods) and customization of the gaming apparatus that is unique to the platform. Where it the hassle with hardware setup anymore? The one I'll give you is calibrating a controller. For couch controller mode there is no plug n' play like consoles. Otherwise, PCs have been simplified in the same fashion, now.
Your hassle is that you have one TV (with too few ports) supporting too many consoles. You also don't seem to understand that almost any TV today will save custom profiles that you can set up so you don't have to re-calibrate settings every time you change them. These TVs often don't default to the correct profile for the Xbox or PS4, anyway.
You will have to change it from "Movie Mode" or "Automatic" to a proper gaming preset-- if there even is one. Neither the console nor the TV are guaranteed to figure that out for you.
LOL, an AppleTV
is an HTPC (so is the Roku). You didn't replace your HTPC with Plex. You replaced your HTPC with a lesser HTPC. Your HTPC could run Plex, too, via Windows OR Linux. I don't understand why you have 3 x HTPCs.
@MUSTKILL, your are an interesting cat. You always seem to understand 90% of what you're talking about, and 90% of what you own.
The PC gaming market is bigger than all console gaming markets combined. The money is just less concentrated in major franchises.
The Console Buffet is a like an alley with a dozen fast food franchises like McDonald's.
The PC Buffet is more like a bazaar with several hundred food carts and local restaurants with only a few McDonalds amidst them.