[Imp]

Its a bit tricky with MBT due to the large timeframe involved & hence units with vastly different capabilities.
Using the US OOB for example an attack helo from the 1970s like the Cobra is an entirely different animal to a 2020 Apache.

Probably easier to set up battles at different timeframes with a view to grasping how the different stats effect the use of units on the battlefield. I would learn ground units to start & set air off.

Infantry does not change much from WWII but most other units do, they really just gain RPGs so become effective vs armour at longer ranges.

Try battles jumping forward in time using the major powers to see how advances in tech effect the way you use units.

As the tech & accuracy increases so does op fire for example in WWII you hit & run or pick opfire opportunities for tanks with care. Late ERA tanks are far more accurate opfire is therefore more useful. Learn how good giros let you move several hexes & still fire with reasonable accuracy.

Another example try using IFVs - APCs equipped with good stats & an auto cannon. You will find these very helpful against dug in units compared to WWII APCs because of the accuracy.

ATGMs a heads up as a bit complicated - to start with they are not a major problem as not very accurate so miss fairly often, early ones have an accuracy of 60 late ones approach 100.
Close in defence systems also seem to work better vs older ATGM models.
Test a bit but for most ATGM's accuracy is different to other weapons as a rule of thumb they are most accurate at above half there range.
Example range 40 ATGM preferred engage range is 20 - 36 hexes it becomes less accurate at close or extreme range. To complicate things top attack ATGMs also often fail to hit the top at ranges over 30 odd hexes.
Also be aware they have a minimum range on some early ones that can be quite large so read the stats. Its normally 2 but can be as high as 10 hex minimum range.
Vehicles with stabilisers can move a hex & fire ATGMs with reduced accuracy based on the giros capability.

Late Era you have to be aware that while not common vehicles can be shot at from 60 odd hex range