Welcome to the forum!
I have my R3 Metas in a 20sqm living room and they provide a decent overall response. Not at all ‘too much’ for the room. The question is rather if you want to add a sub in addition, not if they are too much

. I can imagine the LS50’s would work well too, but the R3’s should have a bit more kick/foundation down low.
I currently use mine without a sub, but did have an SVS SB-1000 for a while and that certainly added to the experience; lowest octaves for music and of course something extra for movies. (The sub is repurposed to a different system that needed it more). But I am quite satisfied running them just 2.0. Just depends on how much/deep bass you want.
So, for LS 50’s; you might want to add a sub.
And for R3’s; you still might want to add a sub.