I finished a germany game here are some observations and tips.
Started 29 october 41, encircled soviets down to less than 100 divs by March 42. Took 100k casualties for 3.5M, at this point I activated battleplans for infantry since sovs no longer had enough to cover the entire front.
240 x 20w inf, eng, cav rec, art, aa, logi
72 x same for Atlantic wall + baltic security
2x4 x 40w medium tanks, 13/7 eng, armor rec, signal, maint, logi
Tank was close support gun, 3 man turret, imp radio, 2x heavy mgs, wet ammo, torsion bar, weld, gas, 10/2, not optimized by any means I don't think.
Could have switched to mech but didn't bother, I think would have been good idea though. Soviet tanks couldn't fight because of supply issues, this strategy should work well against all AI's. Again human you need TD's to counter enemy armor and need to go down heavy guns as well, close support gun is really good for the start but it would suck against reactive player.
Tank chassis are noob traps in SP, base chassis was good for me the entire game, the advanced versions give reliability and armor but neither of those is needed.
AA tank extremely useful, I was being memed by soviet air when ever I didn't use mine to dominate.
Air is extremely powerful, I refused to use logi strike, just cassed my way to victory
Attack along railroads with your spearhead
Railwayguns are good, bring few, they don't stack, I just had 1 on every army, 20 in total.
Attack one supply depot at a time, if you can approach from 2 directions and encircle the area between the railroads. If not just take the depot with a snake and then wait till you convert the railroads.
Use air supply, I had 2 groups of 20 planes to follow my 2 groups of 4 tanks, which pushed the depots
4 tanks on the railroad, hit staff office plan, push with air to depot, clear pocket with infantry, repeat. The timers work pretty well so the supply stabilizes as you are ready to move on. I used 2 groups for faster clears