I'm glad you like it!
The actual combining of the mesh is multi-threaded, but the process of evaluating the ruleset is not. I fully plan to make it much faster at solving tiles, but I have a lot on my plate for the time being. An indie studio contacted me asking about allowing for much larger tilemaps, and sense they're paying extra for it, that's what I'm working on as of writing this.
I may host documentation online at some point, but it's not a priority as of now.
Thank you for buying MAPGrid!