I always get a rental car, but it may depend on how comfortable you are driving on those tight, narrow roads
and being on the other side of the road. I have a British drivers license, and drive over there 2-3 times a year, so I'm very comfortable :-). You can quickly get up to speed though, so I'd recommend a rental car. Having said that, excursions are awesome too. If I were you, I'd do both.
For lodging, there are loads of options. What's your price ranges? If you are taking a day up to the highlands, stay at a bed and breakfast. If you are staying in Edinburgh, my current favorite is Old Town Chambers (
https://www.lateralcity.com/property/old-town-chambers). It's right by St Giles Cathedral. For Glasgow, my current go to is the Raddison Red. Nothing too fancy, but right where I want to be when going to Ibrox, etc and easy access to the M8.
When are you going?