If you are Germany you need more ARM in your divisions in most cases. Running the doctrine plus Germany's ministers means you can weight your panzer divisions towards more armor and less infantry.
The MECH and MOT are there to provide some defense and ORG, but the ARM and SPART are there to provide the firepower, breakthrough, and hardness. That is where panzer divisions really shine. Even if the enemy can pierce your panzers, they are still in deep trouble if your panzer divisions have high hardness, high breakthrough, and high firepower.
Here's a good started 40 width formation. This template shows stats with Panzer IVs and most (but not all) of the mobile warfare tree completed. No XP on the vehicles, and no ministers.
View attachment 262997
Even without MECH, it has a hardness of 68%. It has plenty of firepower and breakthrough. The speed will be better once you appoint some ministers. And it has enough ORG to stay in the fight for as long as it needs to. If you upgrade to MECH, it gets some better stats, including 77% hardness. But MECH is so expensive, especially early in the game, that I find it prohibitive for mass inclusion in panzer forces until later. (There are some issues with speed on MECH I, but that's a whole other discussion.)
The MAINT is there for keeping the equipment from facing breakdowns, the LOG is there to keep your division in supply, the ENG is there to help with terrain. And the Recon is there to speed the division up on open terrain.