[FASTBOAT TOUGH]

I'll give this a try...
First "FH" would normally mean a Field Howitzer/or Towed Artillery.

HE rounds work well against infantry, artillery, trucks and similar vehicles, AA, some SPAA/SPA, some light APC/IFV types. Suppression of these units would also be accomplished with HE rounds, this might include some tanks as well but lighter ones generally speaking.

AP is designed for heavier armor units and hardened positions such as forts. They generally though can be devastating to the units above as well. I personally prefer this against larger concentrations of infantry loses are higher when I can catch them in the open.

On an assault I would prefer artillery with the capability to use both ammo types. AP for where I suspect armor might be providing cover/or over watch for the troops in the trenches. HE for troops with some AP for good measure if I have the resources at hand.

I DO NOT concern myself with the "artillery overload" in an assault the end result is more important to me. That being said, you must balance out your forces, if playing the AI YOU WILL encounter a heavy concentration mines therefore you'll need enough engineering type units to support your assault with enough artillery type units to suppress the enemy forces along your line(s) of advance. The "pivot point" or "balance" is up to you depending on the make-up of your core and support ground forces and expected enemy forces and disposition on the field. I will always consider the terrain in front of my "jumping off point" as well for maneuver and evaluating the places to fire on with my artillery.

In a battle just finished, the Russian AI rushed his armor to a group of victory hexes in a stream bed down a "gully" though my arty and one MBT managed to get most of the tanks, this one T-72B3 was sitting against the hill and was over watching about three of his victory hexes my infantry was fighting hard to prevent his infantry from supporting the tank. I knew my tank would be destroyed if I moved it to a firing position. It took several turns (~10) before my AP arty finally took it out due again to the terrain it was sitting on and around it. I also suffered the loss of an APC, Ammo Carrier and killed 3/4 of an Infantry Squad.

I hope this was somewhat helpful to you.

Regards,
Pat