There is a wide choice of electric bikes. I have tried a small wheeled electric-assist bike.it was not very heavy, I have tried ordinary size electric -assist bikes, but not an ordinary electric bike. With an electric-assist one you would always have to pedal, but it is much lighter to pedal than an normal bike. There are straight forward electric bikes, which are probably heavie, that let you have a rest from the pedalling,, In Holland, where only the assist version is considered a bike, the other one is classified as a moped, these bikes are very popular with older people. Some hotels there offer a weekend break for a couple of days Bed, Breakfast and Dinner + the loan of a such a bike for the duration of your stay. An excellent way of trying them out.
There has been some research done into the benefit of cycling. One research, in the USA, was about tandem cycling (Forced Exercise and Parkinson's Disease 2011), the other, in Holland, looked into the phenomenon of being "off", so unable to put one foot in front of the other, let alone being able to walk any distance , but still being able to cycle . The only snag in this case was getting off and on the bike, which can be tricky, I have experienced this.