I guess you could even test this, by running GeForce Now on all computers vs native.
If not for the PCs, you would still need some devices to run the games.
I tried Stadia once. Played Celeste. The results were very interesting. I didn't exactly perceive latency, but I did perceive that the game felt wrong. As a result, my favorite game of all time was not fun when playing on Stadia. If I didn't have the local version of the game to compare against, I would probably have blamed the game, because again, it didn't feel like latency was the problem.
I dunno, maybe that experience was skewed by the fact that Celeste is probably one of the most timing-sensitive games out there and I'd played it a lot... but now I'm worried that anything played via one of these streaming services is just going to be subtly less fun. I think I'll stick to local gaming.