Germans get panzerfausts off the bat, they're very useful as flamers don't have that much more range than them. The .50 cal on the M3 is annoying but not much else. MG-42s on either infantry units are effective, a panzerfaust followed by sustained fire will destroyed the M3 and cause massive casualties to those inside. armour piercing rounds on vet 1 MG-42 will wreck an m3. In the longer term use a 221 yourself, the 20mm cannon upgrade will wreck any remaining scoutcars.
The Soviet Sniper, whilst difficult to countersnipe, cannot countersnipe you if you snipe from cover. Snipe in cover and you'll recloak before he can get a shot. Use this to your advantage. DO NOT run the sniper around in an open field where he will be shot. The German sniper camos absurdly quickly, so use that to your advantage.
Don't think that fireup makes Cons unsuppressable. Suppression stop them dead, the MG-42 is your friend, but keep grens near it. If Cons ura up to it to throw a molotov, move or retreat the MG and in that time the grens will have damaged the cons enough for them to be defeated by your grens.
About your second point I have some questions. I tried the german sniper and it works okay against soviet snipers. It really forces them to fire less freguently allowing you to move up. The vet1 is quite nice but still does not guarantee a wipe and has long aimtime. I just have some questions:
If german sniper fires at a con squad from cover. Can the soviet sniper countersnipe fast enough or does the german sniper cloak first? What about when you shoot at a soviet sniper who hasnt shot yet?
I ask because from my gameplay the sniper sometimes doesnt cloak fast enough and gets countersniped after example 1 but sometimes he does cloak fast enough. Maybe it is because the enemy targets my sniper too late?