Unsupported tanks behind enemy lines

[Imp]

Re map size its been discussed elsewhere but I agree with Cross in most cases your map size should correspond to the size of your force. You are tasked with this bit of front & other units are on either side of you dealing with theres.
Vs a human changing the size adds variety as you both adapt.
Vs the AI once you start getting to big real estate vs units involved the advantage goes very much to the human. You are spread out but so is the AI but the big diffrence is you hopefully exploit this well by getting localised force superiority while the AI does not react well to this keeping pretty much to the plan.