You nailed most of the thoughts. Double headache!
The 2v head design far exceeds most 4v head design in terms of port angle relative to the valve angle all relative to the bore axis. 4v Tumble in cylinder motion does not compare to 2v swirl in cylinder motion (like a cup of liquid stirred, step back and watch how long the motion will last). In other words, most 4v heads dont offer the best in cylinder motion. Now the aviator, 04cobra, or fr500 4v heads....change the game. And how to look at this? Ill try to explain. The early production C 4v heads had ports that create a high tumble. These port laid nearly perpendicular to the bore. (all 4v heads produce tumble motion...like water pouring into a glass cup and 2v heads produce swirl....like a vortex tornado stirred in the cup) As the piston draws incoming rush mixture, a high tumble head will produce very strong tight tumbles directly after the valve that rampantly will slow down following the piston as it reaches the bottom(the motion at the bottom is slower than the tail end rush thats at the top). This is mostly due to the tumble being non-axial to the bore and the tumble itself is really tight staying at the top.....perfect for emissions!
The better 4v heads ports are raised angling the rush toward the bottom of the bore creating big tumbles that completely cover the depth of the cylinder. This improves the mixture greatly, even though the mixture technically is slow....its more uniformed.
2v regardless of port shape creates an axial motion to the bore. We will call it swirl. Their are a few controlled patterns of swirl, but we wont go into that. Lets just call it swirl. Take the glass of water, stir it real good, step back and time the motion. Its movement is axial to the bore with no complications to move like tumble would be.
This is why direct injection was soooo needed. No port and valve wash down and the direct injection itself creates mixture with in the bore keeping the mix moving while piston nears the bottom.