I've been a few times and like it very much. I like to bring my own tie downs for the ferry because their ropes are always really dirty and I prefer ratchet tie downs. I'm not sure how the booking for the ferry is now, but I used to book in advance during the mid-summer season. Bikes get loaded on first and are first off.
For roads, nothing is technical or twisty, but more straight or slightly winding and scenic. IIRC the roads were bumpy and many gravel roads around there too. At the end of many of the roads there are things to do like hiking or checking out the alvars, etc. I would suggest you 'do not' stay at Gordon's Lodge - there were reviews that it was bad and I can confirm it was one of the worst places I have ever stayed in. For camping I have stayed at Green Acres which is on the east side of the island which was okay - a good number of RV's, but it's also right beside the water with a big beach and some crappy food for dinner. I did stay at a place called L'Auberge Inn which is a house that feels like a BnB, although they call themselves a hostel. Very gracious hosts and bike friendly, with kayaks and other stuff.
For an overnight trip you may not get to do much, but it's still worth it to go. If you can, I would suggest spending 2 nights there so you have a full day to just explore and then you have the time to ride north out of the island into Espanola which is a remarkable stretch when not under construction.