I "think" you should try step-through frame before everything else. This is what seniors prefer, with all those stiff joints. About 200W limit - can't say for sure. Most of AU allows 250W though in Victoria it recently was 200W as I recall.
Hi, Janet. I'm an older (57) woman rider in New Zealand and bought a Specialised Turbo for my commute (14km each way)., That is probably overkill for what you're after -- I used to be a really keen rider so I wanted a faster bike. Like others here, I suggest going to your closest bike store that has at least a minimum range -- e.g. a basic step-through, plus a couple of other more advanced models, and just try them out. I think it's worth buying local if at all possible. They are great fun and you will enjoy your e-bike!