To borrow GF's template
On Media:
Regroup armies-Off <==
ON bc you can always un-group, but never manually regroup; YMMV. What it really means, is that at a glance view of the map, multiple stacks appear as one stack. Clicking on the "top" stack however, puts all stacks into the Stack Panel, each on their own tab, the same as clicking on a stack in a region with multiple stacks, so there is no difficulty in seeing your stacks. It will simply not be as apparent when you glance at the map, but you ought to know where your stacks are anyway.
Battle attrition-Low (as you mentioned, high just hurts the underdog) <== GF?

I can't find this setting, and honestly don't know it. I only know "Attrition" under Game. Help?
Pause after battle-On
Game:
Fog of War-On
Delayed Commitment-Low
Foreign Entry-Normal
Historical Attrition <== furthest right. It is historical for both player and AI.
Auto-replacements-Not
<== I believe is VERY important Do your homework. You will be less confused.
Battle planner-On
Activation-"Land forces with a non-activated commander have a high chance of NOT being able to move at all."
(Some folks like Veteran) <==
Second from left (large movement and combat penalty if not activated) bc you are already penalized with McClellan and his like enough IMHO. I've played with hard activation vs a human. It just feels really unrealistic to me if you have for example 2 corps and only one moves to attack, while the other sits back an watches you get slaughtered. If you attack with unactivated stacks, you're gonna get your ass kicked, but it will be your choice.
Randomized Generals-No
Naval boxes Handling-Standard rules
Extended pool-Historical
Easy supply-Off
Traffic penalty-Low
AI
ActivatedRanking-Colonel (Please do as you wish) <==
Leutnant, bc I feel that it's closer to Real™, where with Colonel Athena is simply cheating IMHO
Use all behaviors-On
Activation bonus-Normal
AI detection range-Low bonus (a higher setting may have the AI do strange things)
Aggressiveness-Normal (as above)
Yup, that's about it. And I really would suggest playing a human opponent , who is closely matched to your experience. It really is the most exciting thing, really.