I also made tests, I find that the scene is rather well optimized after all depends on the configurations for my part I receive 44 FPS with the scene of INI and 45 FPS with the scene of ASOBO of LAX with Fenix A320.
I activated FSLTL and there my performance dropped to 30 FPS or even 25 FPS depending on the number of flight plan.
Clearly they did not test at all with FSLTL
Spect: RTX 2080 Ti I9 9900 K 4.8 Ghz 64 Go Memory