At least for myself, using some of the fancier 80/90 gsm sheets in that list (Clairfontaine for one) only makes sense if I'll be taking my notes with a fountain

At least for myself, using some of the fancier 80/90 gsm sheets in that list (Clairfontaine for one) only makes sense if I'll be taking my notes with a fountain pen (which can be a lot of fun!), but with rollerball/ballpoint I'd get the same experience from the cheaper Rhodia options, that would probably be just fine at preventing bleedthrough (some of the fancier papers can be really good at preventing feathering in just how well they render present some inks).