Wait, since when did X11 have a screen tearing problem?

Like yeah, if you're not running a compositor you're gonna get screen tearing unless you turn on TearFree, but a) hey native triple buffered everything! (except on Nvidia because Nvidia doesn't care) and b) all of that is moot if you do run a compositor. That said KWin on X11 has frame pacing issues so disabling its compositing to play games is a good idea. You don't have to do that on Wayland. Also c) games can totally do vsync themselves, can't they?

At least you CAN do xorg.conf stuff. With Wayland, if your DE doesn't provide you a scroll speed slider you're just fucked.

And about "security"... sure, if malicious apps on your system are even part of your threat model in the first place. It makes sense for phones. On desktop though, most malicious stuff is probably confined to your web browser anyway. I'd rather have working copy-paste and window control scripting and suchlike.