P3D dejavue…
Btw, again, i absolutely dont think this has to do with the beta. Maybe it got worse for some but this issue (like so many others i see popup in beta forums) are long time here already.
I can show you the exact same behaviour and ive never joined a beta yet.
Example KSAT from Inibuilds, i just did that flight yesterday, with cleared rolling cache and scenery indexes. If i load in at KSAT and fly around the airport i never get below 45 fps and near to no microstutter.
I can pop out GSX vehicles, the fps wont budge.
If i fly here from MMMY (that was the case yesterday, in the Fenix A320) i arrive in hefty stutters with less that 20 fps. Its even freezing for some 100 ms here and there (like all 10 seconds). I dont have pics sadly but next flight ill do them.
Again, the situation was like this:
- load in at KSAT in the Fenix 320 on gate XY.
- spawn GSX
- start flight, depart
= nothing happens, very good fps over 40 and nearly 0 microstutter
- load in at MMMY in the same plane
- fly to KSAT
= fps below 20 and hefty microstutter when approaching the same area you had 45 fps on departure
- taxi to same gate
- spawn GSX
= fps below 15 and even more microstutter.
- restart the flight
= back to over 45 fps an no microstutter
Its same in P3D, it was like that there too. But MSFS was long time free from this, it was the very issue i went to msfs (this and the scenery layering issues all the time), now since a while we have it here too 
RTX 2080TI with newest drivers
i9900K
no overclock anywhere
32GB RAM
16GB Rolling Cache on an NVM SSD.