The resolution, if you used the 1280 patch, is 1280. The patch locks the resolution at 1280 which is why there are no other options available.
In addition to changing the resolution, the patch also tones down the skid sounds, reduces the braking efficiency and loosens up the traction.
If you want to run at a different resolution, start with a fresh (unpatched) archives folder and apply one of the other patches.
(You can run a patched version of
SoS at 800x600, but the mirrors won't be present. The main point of the resolution patch was to properly locate the mirrors at higher resolutions.)
Glad you got it working! Happy New Year!
