Howdy and welcome.
Best bet for ease of pedaling with no drag might be a friction drive, IMHO. But like every thing, there are pros and cons. Would read up on em and look for folks who have one. Some times folks who haven't owned or ridden one have strong opinions that don't properly reflect FDs.
Thing I like about em is ya can just switch back to a bicycle only drive with no drag. All the noise and vibes are behind you and can be a 4smoke with regular sized cranks, if ya wanted one. But then there are always compromises. Biggest one is not good for wet road conditions if you need to motor. But you have many options! Some great kits and DIY ideas to be had.
I have done a road bike or 2. They are fine. road bike - Google Search
Gives ya lots of room for an engine, IF. (inframe)