Brooke, these two issues should be kept separate. The have no tangible reason to be linked.
The 109 business is just because of a suggestion to do it that way.
This is flat out incorrect. Sorry to be so blunt, but this needs to me made perfectly clear.
This is an accuracy issue just as much as a playability one - and in either case, is satisfied by having the 109 types mixed.
Bf 109G-6 production began in February 1943 - the exact time frame this scenario is set. No unit in the Luftwaffe had exclusively G-6's until summer. The earliest reference I have seen to the definitive use of a G-6 in Tunisia is the death of Joachim Muncheburg on March 23. If any G-6's were available in February, they were in small amounts, and dispersed between units.
As for how the choice affects playability, the performance between the G-2 and G-6 is small but noticeable (similar to the difference between the P-51B and D) where one sacrifices some speed and maneuverability for improved firepower. But some prefer feel of the G-6 due to the heavier nose, making it more stable.
As for the Spit9's they were not used by the 12th AF until April '43. So their inclusion is not accurate.
The Spit9 affects playability by becoming the best overall plane in the setup. It matches the speed of the 109s and 190 above 15K, roughly matches the G-2 (best Axis climber) in climb rate over 12K and out turns and handles better than the 190 or 109 at every alt. It has twice the 20mm ammo as the SpitV. There is no meaningful weakness inherent to the Spit9, whereas every single other plane sacrifices some meaningful ability to gain an advantage somewhere else.
To be both historically accurate and playability balanced, the answer is to have no Spit 9's and mixed G-2's with G-6's.