Soviet BO vs Ostheer : Conscript, Conscript, Conscript, Molotov, Conscript, Doctrinal Infantry (Shocktroopers/Guards depending on the map) or PPSHs. If your doc has late game armour, just keep harassing with your 4 conscripts and (at least) 2 squads of doctrinal infantry until you're ready to field heavy armour. If not, spam T34s.
I see this strategy 90% of the time regardless of map or prior knowledge of your BO. Some people are a little more interesting with early T1/T2 but the safest way to play a 1v1 is generally conscripts and Guards/Shocks.
Soviet BO vs OKW : (If you're on an open map) Sniper, Scout-car, Conscript, Sniper, Guard spam, T34/85s (Barton Approved
)
American BO vs Ostheer: Rifle, Rifle, Vet Rifle, Ambulance, Lieut, M20, M4A1-AAHT, Captain, (Optional) AT Guns, Ez8s (Or Standard rifle instead of Vet Rifle and Major->Jacksons/Shermans instead of Ez8s if you don't have rifle company). This strats virtually unbeatable at the moment unless you get insanely lucky with a tellar.
American BO vs OKW: Rifle, Rifle, Rifle, Ambulance, Lieut, MGs, Captain, (Optional) AT Gun(s), Major, Jackson (Or Vet Rifle instead of third rifle and Ez8s instead of Major/Jackson).
Ostheer vs Americans: Gren, Gren/MG42, Gren, Gren/MG42, T2, PaK, Pgrens, PaK. Never, ever use non-doctrinal armour against the Americans unless you
actually have superior map control (Which if you can pull off against the Americans on anything other than Langres against a competent player going the standard American vs Ost BO, you deserve a medal). Generally transition into either a Tiger or, if you've gone Tiger Ace, PIVs into Tiger Ace.
Ostheer vs Sovs: I feel like this is one of the few matchups you can't really go into a game with a single, preplanned BO. There are quite a few which work equally well. Both doctrinal and non-doctrinal armour are valid choices.
I'm not even going to do an OKW BO list because there's such a variety of shit you can do which'll work.