GB Studio is a joy to use. Helped in part due to it's limitation I guess. Some key things about this project and how I did it:
The large character sprites are made up of many small sprites that I manually cut up and shifted about to fit, each assigned to an actor.
The tiles were drawn as whole scenes which I then measured the tile count of with https://gb-studio-tile-count.glitch.me/ and optimized from there. The tile count has to be under 192 or something like that. My main goal was to achieve the 3D-esque scenes.
Each dungeon is a large image made up of the smaller scenes and movement is done by shifting the camera around to each area.
The movement is done by using a small set of invisible triggers in the corner of "chunk" of the dungeon; when you move, it hits a trigger that moves the camera by a certain amount (basically screen width or screen height)