Brad,
I stayed in 1500 earlier this month. It is more centrally located just across the road from the Meadow Trading Post area and main pool. It has a bus stop right in front of it on the Yellow internal bus line. It has 21 sites and shares a Comfort Station with 1600 next door. Sites are generally smaller than 2000 but has a few big ones. We request 1500 whenever we book a Tent site. (We add our request via a call to the reservation line and ask the CM to note our request for 1500 on the reservation. It has been there each time and I also make the request in person when I arrive and check in).
Loop 2000 is not as central, a little further away from the core Fort area. It has a bus stop on the Purple line (which comes down through the main cabin loops too). It has 69 sites served by two Comfort Stations. The sites are generally bigger so it's usually recommended when people have a huge tent or want a big site.
IMO the 2000 loop can get crazy with multiple families staying together (since sites are bigger, multiple tents can be used) and the place can become full of kids, cars, and noise at times, particularly on fall and spring weekends. This month there were multiple families on one or two sites in 1500 but they were not crazy. Since most of the sites are smaller, they tend to only support one camping group.
For a bike rental, there is a shop in Celebration close to Disney on the east side of I4 that rents bikes by the day or week with delivery included with a week-long rental.
https://www.evolvebikes.com/articles/renting-a-bike-pg65.htm
For those who don't know, Disney/FW also rents bikes at the Bike Barn near the main pool but on a daily rental basis only so bikes have to be picked up and returned every single day; they cannot be kept/rented overnight.
Bama Ed
PS - Agree with the 2100 loop statement by Denise above. As background, 2100 in the 1970s was installed as a camping loop like 1500 and 2000 but later the sites were paved over and cabins were put on it similar to the cabins in loops 2200-2800. But two years ago due to the high demand for campsites (and excess cabin capacity to meet cabin demand), 2100 was converted back to a camping loop and the cabins removed. However, the sites are mostly a single long narrow (not Premium site width) paved spot with little or no coquina for a tent pad.