The older not-Aero-Snap feature has the ability to move the cursor to the edge of two windows in order to quickly resize them, however this is not true for the custom tiling feature implemented in 5.27.
Clarification - specifically the ability to resize without having to press Meta+T to enter custom tiling mode first.
It does in fact have that feature. Can you attach a screen recording that shows it not working for you?
Ok, so after a bit of testing it seems that it's specifically Chromium-based browsers that's buggy. Google Chrome straight up doesn't work unless using system title bar and borders - except it does work with the older Aero Snap, peculiarly. Also of note is that custom tiling click-to-drag does work with non-Google Chromium and Brave, albeit with some graphical glitches.
Created attachment 156581 [details] Demo of custom tiling (or rather, not) in Chrome and Chromium
Update - I deleted my ~/.config/google-chrome folder and the good news is that click-and-drag now works. The bad news is that the resize lag is still a thing, and whereas before Aero Snap was free from the issue it's also suffering from the bug now.
Closing as issue seems to be resolved; I am now able to resize Chrome windows snappily both under XWayland and Native.