[onion2k]

You don't really need to err on the side of caution, you can just try some of the examples. The first example, https://i2160.csb.app/ runs well on my $120 3 year old Android phone. My instanced ducks example, https://os16k.csb.app/ only gets about 15fps but its doing more than most games or sites need albeit in a trivial way.

react-three-fiber isn't a magic bullet that will make all web 3D things fast. You still have to be sensible. It does make it much easier to prototype things though, and a lot of the time performance is great. And if it isn't then most of the code is quite straightforward to move to pure WebGL.