Best advice is to just try it with GStudio.
All your questions are reliant upon you simply undertaking the project.
At present GStudio cannot be ported but having said that, porting is reliant upon an exceptional programmer regardless of the engine used(ie. it can..).
Bitmap fonts are always reliable but cannot be scaled like tt fonts, they are always squared per digit.
Shaders are eye candy and should be used only when you absolutly have to.
So step one, decide for sure what engine you want to start this proj off in and if its GStudio, we'll take it from there but be prepared for a whole heap of 'CAUTIONS'

Go hard out...