UE5 low fps and stuttering

I know this topic has been brought up before but I’m having a very odd issue on my laptop (i9/64gb/4090 mobile) where both UE5.3 and 5.4 won’t run any faster than 60fps and regularly drop down to 15fps when I start moving around a scene. For the record this happens on the basic starter map in any display mode I try: light, unlight, wireframe, etc. so I don’t believe this is a lumen/nanite issue. Besides, this machine is plenty powerful enough for any of that. This also happens when editing blueprints, its feels slow and clunky. Ditto for the menus, I can see a visible lag between highlights and my cursor. In short, something seems to be bogging everything down, not just the viewport.

Here’s the interesting bit (to me at any rate) when I run UEFN I’m getting a rock solid 120fps on far more complex maps. Given the tech is more or less the same under the hood it makes me wonder if there’s a setting somewhere in UE that I need to edit?

Any help would be appreciated, UE is my daily driver/full time job and I’m going kind of nuts trying to get work done!