Finding MTB routes in Europe

I'm a road cyclist (mountain roads mainly) but I'm in the midst of a mid-life crisis and I'm trying to work out what's best to do.

I have more time and less fitness than I have had, and I'm planning to do a lot of touring in Europe: Pyrenees, Alps, the Europas, Galicia, using an electric bike so I can extend my activities without killing myself.

This leads to an existentional crisis: should I actually cross over and go for for an eMTB? I'm guessing that an electric off-roader might be a lot of fun.

How easy is it to find good off-road routes when touring? Are there good guides with grading like there are for walking? Is there any ill-will between MTBers and walkers?