-MGs are your friends. All 3 allied factions will outnumber you with infantry, don't be afraid to extend T1 a bit and get a 2nd MG to stabilize the frontline. On urban maps, a mortar might be useful instead, the Ost mortar is a killer.
-Keep grens in pairs against USF/UKF. They will more or less always lose 1v1 fights on their own, you don't want that.
-Use your starting pioneers! Can't tell you how many times sneaking in a pio squad helped tip the balance. Their DPS is acceptable up close, so try to have them support your grens early game.
-Move your MGs. If you see a smoke grenade, pack up immediately and repostition further back. If you see Ooorah'd conscripts and can't reposition in time, retreat. Losing your MGs is a death sentence.
-Consider getting PGrens if the early game went well. They can take some hits and unlike Grens can win 1v1 engagements, and also plug Ostheer's weakness in urban maps.
-Panzer 4 is only worth it if you comfortably won the early game. Otherwise getting a Stug is more prudent. You might hurt on anti-infantry a bit more but a properly supported Stug can tackle anything short of Jacksons or Comets. A pair of properly used Stugs can handle any single allied tank.
-If you start to fall behind, take territory one at a time. Have your MGs in an overlapping field of fire. The longer you're driven off from the field, the more muni your opponent has to fuel the doomblob and the more fuel they have for the medium tank onslaught. Better hold on to 50% of the map comfortably, than try to hold on to 70% and get beaten back by a strong push.
Good advices!
Same strategy here, except I was more founded on P4s. But Stugs can be a better options, like you explained, both AT and resource preservation wise.
A small bit of wisdom in a see of garbage.
Thank you.