I'll also follow the bullet point reply to the topic.
Toilet: Yes, easy to swap on whatever you get... unless the toilet is a very short one that sits on a box. Some Class A makers did that extensively in the 90s and some even into the 2000s. That means you have to find a toilet with similar vertical dimensions, or you have to remove the old toilet, the framework it is sitting on, determine how to cover the floor in the bathroom where the box void is and hope that the down pipe from the toilet to the black tank is in the proper place to put in a new toilet. Keep in mind that many of these manufacturers put the toilet on a a box so they could put in an angled down pipe to the black tank because the toilet was not located directly over the black tank.
A/C: Lots of older Class As have two A/Cs. Ducted systems with wall thermostats are most prevalent on anything from about 2000 forward. With two roof airs you have two cooling zones in which the front A/C handles the front of the coach and the rear unit handles the rear. If the coach you are looking at has 2 roof airs, one for sure is handling the rear of the coach.
Slides: Finding a post 2000 Class A with no slides is going to be very challenging. Most manufacturers started to dabble in slides on Class As in the late 90s and the popularity and quantity of slides has increased since then. If you really don't want slides you are either looking for a unicorn or you will have to make your age range for your used coach go back a whole lot farther than 2000. As others have said, a used unit in which the slides work now, can always have some extra inspection and maintenance done which can ensure that slides continue to work well into the future.
Twin beds: That is a pretty rare option to find in older coaches, I haven't seen twin beds in anything more modern in years. If that is make or break you will have to buy new and find a maker that will do a one-off custom order to fulfill that.