REAPER becomes a laggy mess with not even 100 tracks

[lucor]

I don't know if this is an actual bug, but it's a real problem for me and makes REAPER an absolute pain to work with in bigger projects.

REAPER is by far the snappiest DAW I know, and it's one of the many reasons why I love it so much and have made the switch after many years of using Cubase.
Unfortunately that snappiness quickly disappears after I've added some VSTi's. Usually I'm not even at 100 tracks before it gets really bad: resizing tracks feels like I have 10fps, drawing in CC curves is extremely choppy, etc...
Is this common? Are there any options in the preferences that I can tweak to make things better?

My specs:
- Windows 10
- i7-7820X @3.6GHz
- 128GB RAM
- 1x 4k monitor, 2x 1080p monitors

Thank you!