My opinion- I’d still go with the 1900kv. It sounds like most of the mixed surfaces are higher grip. That means more amp draw so harder to manage temps and run time. A 1900 kv motor will move a 1/8 scale buggy as fast as it’ll ever need to go and should give you at least as good an operating range.

FWIW, when I ran 1/8e on medium sized tracks, I used a 1700kv. While the 1900kv was slightly faster than me at the end of a straight, I had more punch than the traction could harness (set my speed control's current limiter to 65-70%), was able to make a 15 minute main on 4,500mah/4s packs.