I *imagine* a big part of it being slower was that I didn't use occlusion culling in DD62. I wrongly assumed Unity was already doing that in the background...
And yeah thanks for letting me know about the stairs. I shouldn't really have the area be accessible right now in any way. It's a nice background scenery prop but the model itself and geometry need to be updated. It was accessible before because the player had a higher step size for stepping up geometry. Every step is modeled and uses the mesh collider for the geometry (instead of just using a ramp which I'll likely do in the future) so when I lowered the player's max step height it made the stairs... well, not really climbable.
I did a quick little patch just now that blocked off the stairs and added in a camera speed slider among some other things.
Thank you for playing and giving me your feedback! It's much appreciated!