It sounds like you're thinking of a game like Command Ops, where you can issue an order to a company or brigade HQ and the tactical AI will handle issuing orders down the chain of command. I do not believe that is a feature of Armored Brigade. Much more like Combat Mission or Close Combat, you are expected to issue orders to platoons and elements directly. For better or worse, the burden is on the player to keep their units moving and fighting cohesively.
If you issue an order to an individual element, it will be detached from its group. Be aware that if there is only one element in the group, issuing an order to the element will still detach it. This will create an additional and unnecessary delay in the orders issued. (This mistake happens to me a lot with recce and HQ assets.)
If you set your formation to march and your movement mode SOP to quick, you should see your units use roads. Some people have suggested using wide formation spacing too help with congestion, but they should path along roads regardless. Be aware that a whole brigade attempting to use roads in the initial minutes of a scenario can quickly turn into a messy traffic jam, but they'll sort themselves out. I try to keep my use of road march limited to getting stragglers caught up or redeploying units through the rear to a different flank. Vehicles are already pretty quick across open fields, and I've had better luck keeping them organized by setting them to use the shortest path by default, then plotting the routes I want them to take with more detailed waypoints. (I use the covered route SOP mostly for infantry.)
No, I'm not trying to issue battalion command and expecting the Bn to then give orders down to companies and platoons. What I'm trying to get to work right is what the manual suggests (and you allude to in your final paragraph) issue an order to a platoon of tanks, say tell it to move in echelon right and watch it do so. Or I want to have a platoon of tanks move in march column along the autobahn. Every time I try to do do either the subordinate tanks go to odd way points and if I click to check on the them, they detach. So, I'm not doing something right.
The way I think it works is I click on the flag and all the units in the formation come up with a green square around them. i should then be able to go and set a way point and then set the formation such as echelon right. But it doesn't seem to work.