Just came back from two weeks in Mallorca. What a great trip. We rented bikes because we did not want to take a chance with bikes getting damaged during transport, etc. We rented Cube bikes from Huerzeler.
https://www.huerzeler.com/en I thought the price was right and the support from the shop was great. My Cube bike was disc brakes with Di2. No complaints.
As for routes. I guess the route everyone does is Sa Calobra. Approx 13k straight down to the ocean and then turn around and 13k back up. Make sure you have fresh legs for this ride. One other ride that is quite popular and that I recommend is Cap de Formentor. Great views and just a really nice ride.
Honestly though I think no matter what ride you do, you will not be disappointed. If you have any other questions about where to stay, etc. just ask.