Is FR really much lower variance than 6max? I mean I'd imagine our HJ/CO/BTN ranges are somewhat tighter in FR because we're folding parts of our range when the pot is opened, and the pot will obv be opened more often with 4 more ppl to act in EP, but I debate whether it's so much lower that it would be worth switching games?

Poker has variance. You can't really escape it. I'd recommend reading 'The Mental Game' though, that could help you deal with variance better.

Also what are your aspirations from poker? Is your goal to improve, move up in stakes etc etc? If your goal is to move up, then you will HAVE to embrace variance and be able to deal with that. The higher up you move, the more aggressive the games and variance goes through the roof.