Hiya Erin!
Welcome to planDisney!
Disney's Caribbean Beach Resort is a very lovely Walt Disney World Resort Hotel to stay in. I see that you are focused on transportation strategies which I consider myself a semi-pro at. This Resort has
two Disney Skyliner stations. One at each end of the Resort. One of the Disney Skyliner Stations is inside Disney's Riviera Resort which you can walk to and the closest buildings are the Aruba buildings. This would be the Disney Skyliner station you go to for quicker access to EPCOT.
The other Disney Skyliner station is located near the Jamaica buildings and across the lake from the Trinidad section. This station is the one you should go to when visiting Disney's Hollywood Studios. Either of the stations can get you to EPCOT or Disney's Hollywood Studios but there could be a transfer to Disney's Caribbean Beach Resort if you do other than what I suggested.
When visiting Magic Kingdom Park, the only complimentary transportation option for you is the
Walt Disney World Bus Service. For this Resort, there are multiple bus stops throughout and you will find one near you wherever you are staying. When a Resort has multiple bus stops you may find that wait times can be interesting. The busses start at Martinique then head to Old Port Royale, Barbados, Trinidad (North and South), Jamaica, and then Aruba before heading to its destination. This can mean that by the time it reaches its final stop at the Resort, the bus can be crowded.
Since you are only looking to visit Disney's Hollywood Studios and
Magic Kingdom Park, I suggest getting any room in the Jamaica section. This way you are closest to the Disney Skyliner heading to Disney's Hollywood Studios and can then cross the bridge towards Old Port Royale and get on the bus ahead of the crowds to get to Magic Kingdom Park. I am unable to find you an official online labeled PDF map of this Resort but some unofficial sources are fairly accurate. There is an
interactive map online and on the My Disney Experience Mobile App but it does not show building numbers. The bus stops and Disney Skyliner stations though are viewable. In the Jamaica section, buildings 44 to 46 are closest to the Old Port Royale bus stop via the bridge/walkway. Buildings 41 to 43 are closest to the Disney Skyliner station that I suggested earlier when visiting Disney's Hollywood Studios. Reserving a particular building is not guaranteed to guests as they are usually assigned right before your visit based on availability and pending reservations. The online check-in process doesn't allow for specific room requests either. I suggest you
call and speak to a Cast Member to see if they can make the room or building request for you but know that this is not guaranteed. You will be provided the room you paid for but the specific building is never assured unless you paid for a preferred room. The preferred buildings are in Martinique and Barbados which I do not recommend for you in this answer. In the end, however, no matter where you end up, it is still only a few minutes' walk to wherever you want to connect to transportation options. You will be fine and make your destinations! Just give yourself at least an hour of travel time no matter which building you are assigned to.
I hope this helps and you have a wonderful time! Happy Planning!
-Nimmy