The first question to ask isn't how well does your game perform on x platform. The question to ask is, how will my game perform on a target customer's device. So that begs the question, what kind of device and OS does my target customer use. Part of that answer lies here:
Unless you're target is something very specific, the best approach is a bottoms-up. For example. If you look at Android OS's over the past year, you'll see that Android 9.0 is really starting to take off. But you'll also see that good ole' Lollipop 5.1 still has a fair chunk of market share. Same thing with Windows OS's. Win 10 is slowly taking over. But you still have a lot of 7.0 users out there (31%). So I know that if I develop a game that runs on old hardware from when Lollipop was released, then I've got 7 versions of Android above that which it should haul ass on. If I write my game on an old piece of Windows hardware (like this Core i3 2.1ghz with 4gb of ram that I'm writing this reply on) that was from the Win 7 heyday and it runs well enough that I don't get frustrated, I'll have no issues on my 8 core 4.0ghz AMD with 32gb ram.
So, pick a piece of older hardware you either already have or can get cheaply that you want your game to run on. Make THAT your 'minimum recommended hardware.' If you write everything with that minimum in mind, it should fly on anything bigger and better.
Now, that being said, compatibility testing is a whole new can of worms.