…and phoc, since it’s based on rootston? 
Both squeekboard and phoc evolved way beyond their initial codebases (and squeekboard even got its parts rewritten into a different language), the projects they were initially based on are just technical details at this point.
Did it? It works on postmarketOS. Only packaging Plasma Mobile on PureOS amber-phone stalled (long time ago already), because Debian Buster is a way too old base to reasonably support PlaMo. It may be within the reach for byzantium though.
I’m using it daily on my Librem 5 (via flatpak).
The battery wouldn’t take charging this fast well - that’s the maximum power the device will ever negotiate from the charger, and that power then gets split into charging and operating (and in practice I doubt that it would ever draw 24W, that’s quite a lot - 10W is usually already enough to charge at full speed while the phone is in use).