I mentioned Amazon only because BD was my first dildo and it was too big for myself. If you already have some experience with "regular" ones i think you can forgo going with Amazon and get a BD. If not though, i do recommend getting some butt plugs. They usually come in packs of three in different girths and they help a whole ton with warm-up stretching before taking on bigger stuff. Plus they help when deciding on sizes i.e. if what you can comfortably take is a 1.8 inch wide plug, then you can use that to somewhat determine what to get on the BD site.

Small vs. Medium really depends. I cant help much there since everyones body's are just so different.

In terms of firmness, i'd say it more so depends on the shape of the toy. The thinner it is, the more trouble you may have trying to get it in or staying put/upright. E.g. the Rex in soft cannot stand on its own and is super floppy. If i had to do it again i'd get it in firm base and medium shaft. But my soft Chance is pretty decent and the softness does help squish the head on entry. All in all, if you are absolutely unsure about it, Medium is the way to go. Its a jack of all trades but it does well with a whole ton of them.

I hope it wasn't too tmi, its just i wish someone told me all this before going in myself lmao. I kinda screwed up my body in a bad way because i went all gunz blazing. Definitely need to go slow and steady, start small, etc. If you already have some experience though youre definitely ahead of me!

Have fun and good luck! And i'd be happy to help if you have any more q's.

edit: just noticed those plugs are out of stock. But they're all the same more or less.