We rented a car from Arnold Clark car & van rental because they are the most affordable, have a great offer, and many bases throughout Scotland where you can pick up a car. We picked it up at the airport. When you land, you call them, and then they send their own transport for you (because it's about a 5-10 minute walk to the base, which is not very convenient with a lot of luggage and along the main road). They are very kind, and since our flight was delayed, they themselves offered to refund about 50 pounds, considering we picked up the car in the evening. :)
We took a Nissan Qashqai, considering our plan was to tour all of Scotland, where you will really encounter all kinds of roads. Driving on the opposite side was a bit challenging but quickly mastered. :) What you need to be careful about with vehicles, if you are traveling with your own, is their low emission zone law when entering a city, otherwise you risk high fines. With rentals, you don't have to worry because all models are newer and adapted to the laws. :)
We wanted to leave Edinburgh for the end, so we immediately headed to Glasgow, where we spent the night, and used the whole next day for sightseeing. Since Glasgow was just a stopover, we didn't invest too much money in accommodation in the city center; instead, we took a modest apartment 20 minutes from the city and paid about 120 euros for two nights. :) We prefer private accommodation where we have a kitchen to cook for ourselves. When we traveled alone, it didn't matter to us, and we mostly ate in restaurants, but now, because of the child, this is much more practical for us. It's also a great option if you go to more expensive countries like Iceland, where food in restaurants would cost us as much as air tickets. For example, one hamburger was about 20 euros. Imagine three meals a day in Iceland, for two of us and 7 days. Prices in stores are the same as ours or even cheaper. :)