Surface Book 3 (15") - Forza Horizon 4 Gameplay (Ultra Preset) 

Yes it's running 1920x1200 at 60fps average, no big framedrops. Running full resolution (3240x1560) it's around 30-35fps, but a few framedrops in the 20-25 fps range not unplayable but not really worth it for the extra resolution. This is with the 15in Surface Book 3 GTX 1660Ti.

@@tzeimet I'm getting about 45 to 50 fps most of the time at the max resolution (3240x1260). Only very rarely does it drop to the high 30s for me, and definitely never in the 20s. This is with the 1660Ti model too. Running ultra settings, by the way (with nothing turned down).

I just got an average of 46 FPS at 3240 x 1260; ultra settings (with one stuttering count) in the Forza Horizon 4 benchmark mode.