In principle it wouldn't be any different to drive home a motorcoach than a school bus but in practice this might be a little more challenging. The reason boils down to what law enforcement is looking for and in their eyes school buses are essentially invisible but the same cannot be said for a commercial coach. Nevertheless, the same things you've read applying to a school bus maiden voyage I would advise in your situation as well: drive the speed limit, obey all signs, only enter weigh stations if it specifically says buses weigh, and please PLEASE check overhead clearances because you'll be taller even than a school bus! Have your bill of sale paperwork in hand during the journey in case you need to corroborate your private sale, obscure any commercial markings on the vehicle (company livery, DOT#, etc) and yes if as you read I recommend a sign in the entry door glass that says, "Bus in transit, Not for hire" to demonstrate you're not attempting to fly under the radar operating an illegal public conveyance.
Now as for license requirement, technically you would need a CDL Class B plus Passenger and Air Brake endorsements. Not sure how lenient law enforcement is in your states if you happen to cross paths but be polite, be honest and explain you're only driving home to convert it into an RV. Most people have no issues anyways but a few who've reported an encounter say the LEO is sympathetic and often impressed. An alternate you may pursue is finding a currently idled bus driver who is eager to make a few bucks as so many charter bus fleets are basically closed now. If the drive is only a few hours that's well worth a cool $100.