When it comes to traversing terrain, you have to keep in mind that Spring:1944 has very small models. This makes map imperfections much more importent, as a small bumb in the ground might block your line of fire (but not line of sight).
This should be accounted for many different units on different levels. Light machine guns really need very flat ground to hit the enemy, certain guns like the ISU tend to fire at the ground due to the gun not having very good vertical freedom.
Most weapons count as ballistic, so fireing from high elevation usually give you a notable range advantage.
Units lose speed when traveling uphill, depending on the chassis type. Italy has alpini infantry that almost don't lose speed when travelling uphill and they have a much steeper maximum climbing angle.
Infantry in general has good tolerance for hills and such, allowing them to use terrain to escape rampaging tanks.
Tracked vehicles have second best tolerance, as the larger contact area allowes for more friction. Most notably, the GBR Churchill VII is outstanding in mountainous terrain.
Logically, a step lower are halftracks and after them are cars, but the difference is minimal.