Chiming in, registered just to post.
i9-12900k
32GB RAM
3070Ti
DX12 enabled
Enhancement addon downloaded from Market.
Loaded in to KLAX with no in game flight plan created, loads just fine, albeit with a minor notice to FPS.
Loaded in to KLAX with an IFR in game plan created, slideshow + extended load time.
Tested at KIAH as well, both cold and dark and "Ready to fly" on the runway, with the same results.
Filing an in game flight plan, at least with IFR, seems to absolutely kill it.