Hi.
You haven’t given too much installation data , but if you’ve written that this scheme works for you…
Btrfs is a bit slower than ext4, maybe that’s the reason; although I don’t play games, but on the SSD (I assume it’s quite fast) I think that these differences are not very significant. Also important is the compression (ZSTD, LZO) algorithm used.
Alternatively, try to install something like this; it’s good tutorial from a community member. You shouldn’t have any problems with it (BTW, you don’t have to install grub-btrfs from the AUR).