Anti-tank guns
First, we'll go over the anti-tank guns in detail.
The PaK 38 is the Axis' players first choice in defending a town against a tank assault. Whereas the PaK 36 is too weak to hurt the best two Allied tanks in tier 0, and the 88 is far too slow to move manually, the PaK 38 fills a nice middle-ground. It's more ungainly than the PaK 36 by far, but much faster than the 88, and is closer to the 88 in performance. Although it will have trouble penetrating the Sherman's front hull at ranges above 300-500m (depending on angle), flanks and rear are all valid targets. Just be sure not to aim for the center of the turret at any range, where the Sherman has a very thick mantlet. Driver and hull machine gunner ports on the frontal hull are good targets as well, but, like the outside edges of the turret, tough to hit at longer ranges. The PaK 38 doesn't have quite the same penetration as the 6 pdr, but, thanks to APHE (armor piercing high explosive) ammunition, if it does penetrate, it deals considerably more damage to the squishies inside.
We should also add a note about the 88 (aka FlaK 36). As some people expressed bewilderment when struggling to penetrate the Sherman, it turned out after some research that this gun uses regular Panzergranate (PzGr.) ammunition, which has markedly inferior penetration capability to the PzGr. 39 used by the 88 on the Tiger. Only later in the war did the FlaK 36 receive PzGr. 39, but by then it was superceded by a dedicated anti-tank gun version of the 88, the PaK 43/41.
The British and French, as we said, received variants of the same gun - the 6 pounder. A high-velocity British design, the 6pdr is a 57mm anti-tank gun firing solid shot AP. It penetrates better than the PaK 38, but its killing power isn't quite the same despite the larger size. The French variant, called the M1, is acquired via Lend-Lease from the USA. Like many French items in the newer tiers, it has to be based on other sources since France was no longer officially in the war at this time and thus not designing new hardware. The 6pdr/M1 has an excellent chance to penetrate everything except the Pz IV G's frontal hull, the Pz III H's turret and the StuG III G frontally.
All the new anti-tank guns are slow relative to infantry or the older guns, but they've become very necessary with the arrival of tier 2 armor. Up north, the PaK 38 finally gives Axis a relatively cheap counter to the Matilda tank, and is very competitive against the lighter armor of the Crusader II and Crusader III.