I'll offer what little I know and what less I can execute. I'm still slightly unfavorable k/d in this bird but love the F and G's (all - but especially the g-14 with the Erla Haube hood and the 14 and 6 with the improved 6 view) for their nice balance of climb, turn, accel, and air-to-air weapons loads.
The 109 has a great climb rate and wicked compressibility issues on the way down at near-500. Manual trim can save you on the pullout. Offensively, it's best to spiral down onto someone's 6 or crossing from above. You can follow and kill or snapshot this way. Roll rate is NOT great like in the 190 but still is good enough, provided you keep your speed reasonable, you can vector fire onto a turnbird from above. Indeed, using this practice, you might as well take the gondos - just don't lose the E advantage because the gondos mean compromised climb and turn.
Speaking of climb and turn, most of the American birds can be easily outclimbed, dependent on initial e-state. The Spit, however, is a real danger in rope attempts. Also, it pays to have a good reversal if you go roping. That's why I don't do it that much - my "torque bunt" still requires a lot of attention. Flat-turning, at least without gondos, is pretty good to the left.
One evasive tactic I've used, with some success: the climbing spiral (with flaps) on the verge of stall. It bleeds your opponent, should he try to follow, of energy that he will not recover as easily as you do in your 109.
Btw, I like the 20's. Grizz is not a mere human, nor are the other 109 taterjocks. I can't hit stuff with that loopy 30 - except for bombers. There is little more beautiful than seeing a single or double tap relieve a bomber of its wing. Generally, though, I'll take the gondos, dive in a slicing attack and kick rudder a bit at 600-400 yards. It is often possible to bring down more than one bomber on a pass in this way.
The 109 doesn't take damage all that well, though, notably, the engine will run oiled long enough to get you back to base. Range is weak, also, but that hardly matters here. Speed is good in the late model 109s and usually offers the opportunity to run or catch.
All in all, I call it my aspirational bird. It's nowhere as easy as, for example, the Spit VIII, but offers, for some reason, more reward and, ultimately, I think, more low-speed craziness to explore (like the reversal or climbing at 100mph on thr edge of stall). That's my student's eval - there are certainly better 109 pilots out there than I but I feel a natural affinity for it that I don't get in anything else.
