I think the problem with btrfs is that it entered the spotlight way to early. With Wayland there was time to work on a lot of the kinks before everyone started seriously switching.
On btrfs a bunch of people switched blindly and then lost data. This caused many to have a bad impression of btrfs. These days it is significantly better but because there was so much fear there is less attention paid to it and it is less widely used.
Not having any lag is physically impossible. You don’t notice it maybe. But if I open Firefox with X forwarding on the same network (1gbe) it is very noticeable for me.
@hummus273 Perhaps not because I’m not trying to game, and I can’t detect any changes faster than about 1/50th of a second anyway so fps faster than 50 is more or less moot for me.