If you set gboard to floating you will be able to reach all the keys. have you tried disabling the old keyboard in the settings, I think that is what you have to do to avoid having to choose preferred keyboard every time. It doesn’t have always on display because it would draw a lot of battery because of the lcd panel, but if you want to you can do as me and use this app https://play.google.com/store/apps/details?id=com.tomer.alwayson or a similar one.