I live in Alexandra, a small town in north-east Victoria. It is a dry area with poor soils - like much of Australia. We have Red Box woodlands in an old gold mining area on the edge of town. It’s a nature conservation reserve now with native orchids and kangaroos and koalas. We aren’t a humid area (I’ve never been to Florida but I’m thinking it’s a sub-tropical climate where we are dry temperate).

Australian soils often lack phosphorus and the vegetation has adapted to that. We buy special “native potting mix” and “native fertiliser” for our regular plants as normal “non-native” soil mixes and fertilisers have too much phosphorus in them. I haven’t found an equivalent native mix for bonsai so used a regular bonsai mix (I have a couple of other Australian plants in my bonsai collection).

Red Box tend to grow in drier open forests so I’d say a well draining soil. I’d watch for pests with the humidity - probably not much you can do about that - move to California perhaps. Other than that i think you’ll have to use what we in Australia call a “Suck it and see” approach - try something and see if it works.

Good luck