The performance difference is one that is worth it. I have never seen Project Explore run so smoothly in my life. Bear in mind that the FPS shown here is from a non-YYC build. The only visual difference is the scaling of objects and the distant terrain. On the positive side of it all, we don't look like a Don't Starve clone anymore which is good because it seemed as though that had set a lot of people off.
Optimize The Baby For Fast Crawling
I spent what little time I've had this past week optimizing every little nook and cranny in the games code. I tested at least four difference ways to render onscreen objects only and used the one that proved to be the most efficient. I re-wrote about 75% of the code behind world rendering. It has paid off for sure.
3D And Game Maker
Game Maker just isn't easy to work with when it comes to complicated 3D functionality such as bill boarding. Not to mention it isn't the fastest engine so doing complex math functions to convert a 3D coordinate to a 2D coordinate based on the projection can be a bit slow.
You can't just force an engine designed for 2D games to perform massive amounts of 3D. It is a bad idea from the start and I would probably be better off with Unity or Unreal if we decided to stick with the 3D.