The 109s really start to get powercreeped in rank IV, you’ll need to start sideclimbing now and 1 mistake leads you to a +8k repair. If you want to know the difference between the 109 K-4 and G-10, the K-4 has an insane engine (lots of climbrate and energy), G-10 is very lightweight so it turns a little better due to lower wing loading but the engine is weaker so it is slower and climbs worse.
190s for you should be the D-12 ( x1 MK-108 and x2 Mg151/20s) and the Ta-152 H-1, skip the A family and steer clear of the Ta-152 C-3.
Mk-108s will make you curse a lot, their ballistics are horrible, imagine trying to shoot down a plane with a 15cm sIG 33 B Sfl, they are slow and have a lot of drag. You are going to miss the 20mils.
Mk-103 only suffers from very poor firerate.
Don’t lose your head over dying over and over, 5.7 and 6.3 are very poorly balanced, and a lot of experienced players like to play meta planes over there.
Your opponents no longer stall as predictably, they turn better (even american props), have better firepower and ballistics and climb on par or better than you.
Don’t bleed your speed, no more fancy vertical manouvers, boom and zoom reign now.
Mg151/20 w stealth belts will be your best friend here, they have a lot more muzzle velocity, since the first round in the belts determines the ballistics of all the rounds in the belt. And of course, is better for surprise boom and zoom attacks since you can spray without alerting the enemy most of the time (unless they use their ears).
Spoiler
(except the ta-152 H-1, if you use flaps on it you can win turnfights if you end the fight quickly enough, its 6.0 because it clubs everything with those, so don’t rip them.)
And play the 109 G-6 if you want the last crumbs of 109 glory you’ll have.
When you need help on the german early jets just open a new thread
Small early german jet tip
They sacrifice everything aspect of climbrate, turnrate, low speed control, ACCELERATION (very bad acceleration), ammo and usable cannons (except He-162) for speed.