GL.iNet do seem to backport specific fixes from the master branch from time to time. But I believe they’re mainly using the stable 23.05 branch, which I would expect to be updated every time they release a new firmware? Otherwise you won’t see a “stable” update from GL.iNet until after the next OpenWrt service release.
I’ve been using OpenWrt for years, so I don’t personally feel as though I’m losing much. But if you’re not familiar with OpenWrt then you’ll find it harder to setup some things without GL.iNets UI. That plus you’ll lose Android/iOS app support and the ability to use full cone NAT.
And as I’ve said before, if you do try a snapshot be sure to build a custom one (click on Customize installed packages) so that it’ll include LuCI. And then once you’ve installed it follow this guide.