OpenSUSE Tumbleweed has great KDE implementation. Best I found and stuck to last time I hopped around.

Rolling release yet super stable. Great configuration tools.

Whatever you choose you should enable zram! It’s a Linux kernel module so available on all distros. It makes a compressed partition on the ram.

I’ve had a ThinkPad with 8 GB of ram and it was night and day with zram enabled. Just used the defaults, no more stutter or hanging for minutes. I used Tumbleweed.