Off the Wall is the only far off-shore resort I've been to (2x), which is out on Glover's reef atoll (Long Caye, not to be confused with another Long Caye closer to the Blue Hole). It is an eco resort, meaning no flush toilets, no AC...sort of like glamping in nice water-side huts cooled by the sea breezes. Owners Jim and Kendra are fantastic and the experience out there is about as chilled as it gets. The diving quality is definitely a full step above Ambergris. Based on your comments above, I think you would be bored after a few days at a place like OTW...since life out there is diving, SUP/kayaking, snorkeling, fishing, book reading, hammock-ing. Nightlife is drinking a beer watching the sunset on the resort dock.
I think most of these off-shore resorts only provide transport once/week. Some are at least 20-30 miles off-shore with a tiny population (largely just resort workers and guests), so I don't think the concept of a frequent water taxi really exists. Maybe others can provide additional info on the other resorts
One compromise for better diving combined with mainland activities is to stay south on the mainland.....deal with the longer boat rides out to the offshore reefs....and then go to AC for a few days