afaik all keyboards work offline, otherwise people would notice very quickly and change.
“Better” is very subjective. A good principle is to try FLOSS software alternatives and see if they work for you first. Often people are using proprietary spyware like gboard because it was the default and that’s what they got used to more so than it’s inherently better. The nice thing about instaling an OS like iodé is that you already get a curated selection of free and open source software. On android stock there is NO ability to stop the default (gboard) from accessing the network, afaik, google is logging finger speed, patterns, spellling mistakes, everything, they even know if you’re sober or not!.