[Imp]

Keep in mind the game takes place around point of contact the unit could have travelled miles. I have never been in the military but I would assume it depends on the expected threat level.
Minimal - convoy with a few fast scout vehicles out front, hopefully they can stop and check out dodgy spots without slowing the convoy to much.
Medium - Same but scout vehicles also running on the flanks, slows you down a bit if assume progressing down a road as the flanking vehicles are not.
High - over watch as described so a lot slower and the column can break up because of this to be in a position to lend support.

Not having dismounts tag along has I think been proven a bad idea hence why modern armies are mechanised. Germany got away with it on the Eastern front when they made a breakthrough, they still tried to scoop up a few men to take along.
Only used half tracks if needed they were not the USA half tracks were valuable as transport to carry equipment in when marching.

Translating to a modern army using USA as they are equipment rich, the composition of a cavalry unit has been pretty much the same since the 60s
Jeep type vehicles as outrunners, troop carriers for the extra eyes the dismounts provide, the armour.
You have more scouts than armour and they are scouts, enough for the whole formation to use bounding overwatch as described with troops always on the ground and armour covering.
Very hard formation to catch by surprise if used correctly and the armour only leads if appropriate and the infantry on the ground have eyes covering or have found targets.