1940 France vs Germany is a very good match.
You’ll need plenty of Char B1-bis (3-4) and 88mm Flak 36 (2-3) becuase it’s the most powerfull unit from that time to stop it. The German tanks are useless agianst the Char armor 5/5. Plus the double shot really hurts. Elite Pnzr IV works but the lighter armor gets it killed quickly. Mechanized infantry is the only way for the Germans to win in my opinion.
The Germans had total control of the air at that time but the German planes have crap anti-tank attack and no special ability to help with the exception of the Junkers but it’s from 1943.
If the Germans are having a problem to win, try adding a plane or two (free of charge) to the German army to even the game. The planes can keep the French infrantry pinned down… historically acurate.
Ebay is the best place to get minis cheap one at a time.