Well, I think it would present a very interesting situation for our various provincial and territorial Human Right Commissions to start ruling on SP postings based on the client categories you've outlined. Lol.
In general, I think many but not all providers would prefer to deal with 30 and up because they are both sexually and emotionally more mature and experienced. Though there are many respectful young men under that age, it's the spoiled "entitlement jerks" produced by money-hungry lazy parents of the previous generation who tend to piss most people off by their generally retarded arrogance and ignorance, and so spoil it for their entire generation.
As for body types, most providers I've talked to are pretty tolerant. I know a woman who's 105 lbs who's accommodated guys who weigh over 400 lbs. Though not in a way that could involve her getting crushed. Lol. Providers also see a lot of weird cock and ball deformations, but carry on anyway so that the clients don't feel bad. Medical text book stuff, like foreskins that never seem to end, one ball the size of a pea while the other is a tennis ball, urethra openings on the side on dick heads, rather than the top, etc. etc.
As for cultures, religions, races, etc. I think it's members of certain sub-groups within the larger groups, rather than generic stereotypes, that turn providers off. And they can come from any culture, religion or race.
For example, members of groups who think it's okay to behead women for going to school, who think it's okay to burn women alive for the financial benefit of their in-laws, who think arranged marriages for girls under 14 is okay, who think it's okay to cut the clit out of prepubescent girls with a piece of dirty glass so that they will be faithful to their husbands, who think it's okay to beat women to teach them a lesson about obedience. Unfortunately, there are lots of examples. And unfortunately, in the examples just given, I think I've covered sub-groups within most major cultures, religions and races.
Male members of those kind of sub-groups, rightly or wrongly, may easily find their way onto many SP "no-see" lists.