The V'll still out turn any of the two stage Merlin Spits, but it lost an awful lot of "oomph". The reduction to +12lbs boost greatly reduced it's acceleration/climb rate. The older drum fed cannons are limited to 60 rounds per gun and that has an obvious effect.
The Spit I was raised in boost to +12lbs from ~+8.5lbs, but I have heard there are issues with it since v2.06 p1, though I've not tested that myself.
The Bf109G-10 was renamed Bf109K-4 (which it always had been in any case, but was fudged up as a G-10 to get the 20mm options). The performance should still be the same, but it lost the options for the gondolas and the 20mm hub gun.
The Bf109G-14 was added to fill the massive gap between the Bf109G-6 and Bf109K-4. It is essentially a late Bf109G-6 with MW50 boost whice gives it significantly better power below FTH of 5000m (16,400ft). It has all the gun options the old Bf109G-6 had.
The Bf109G-6 lost the option for the 30mm hub gun as it now represents an earlier, 1943 version.
The Bf109G-2 had no changes.
The Bf109F-4 lost the option for the gondolas as they were very rare on the Bf109F-4.