I did this tour last year with Travelsphere and had a double seat to myself, so plenty of room, but then I am not 6 foot plus! The coach was the normal touring one (tinted glass, air con and with a toilet) for say 45 passengers.
You will really love this tour as there is so much to see and I really mean that. Because of the number of miles involved, you will be leaving the hotels early some mornings e.g. 7am but each day there is something exciting to see and experience. My favourites were Bryce Canyon, Monument Valley and The Arches but then every day was a favourite. See the reviews on this tour. Oliveb was a very good one.
The weather will be hot in some of the parks whenever you go. If you want some idea of the temperatures go on to the US Weather Channel website www.weather.com and enter the destination.
Have a great time
Regards
Malcolm