# of hands/players
Do you think it is better to play one on one with the dealer or with a few people? And if you play one on one is 2 hands better than one for a counter?
Preface: if you don't already know the answers to these questions, you shouldn't even THINK of playing with $100 chips, which, as suggested by your other posts, you have been doing with reckless abandon. Also, the following assumes that you are a competent card counter.
# of players:
In terms of producing the most +EV, it is always best to play head up, regardless of # of decks, since you'll get more hands per hour. This is particularly true in SD/DD.
That being said, it is nice to play with one or two other players in shoe games, so you can leave for the bathroom, or answer your (vibrating) cell phone, when the count tanks, so the ploppy can take all the crappy cards while you're in the can or talking on the phone. If you're playing solo, the crappy cards are still going to be there when you get back.
2 hands vs. 1 hand:
Going to 2 hands chews up approximately 1.5x as many cards as playing 1 hand, so you would need to bet 2 x 0.75 units to get the same "action" in +EV situations as betting 1 x 1 unit. Thus, your EV will be approximately the same with 1 x 1 or 2 x 0.75.
EV aside, in my view, there are cover advantages to playing two hands in positive counts since it makes your spread appear smaller. In my opinion, two stacks of 5 chips seems smaller than one oversized stack of 7 or 8 chips.
In -EV counts (assuming you are still playing) it is better to play 2 x 0.5 units rather than 1x1 unit, since it reduces your overall action, but this may hurt your cover.