honda supercubs might be a nice middle ground. 70cc with gears but no clutch. it’s basically a semi-automatic.

Generally speaking what I’ve seen is that it’s ok to apply in advance, but I can’t be sure for your particular situation (I didn’t even know that VN did 3 month visas… are you American?).

I recommend posting this on the aseannow or tripadvisor forums – probably the latter, as they’re quite good with visa questions. Or at least r/VietNam