G17 Gen 3 RSA vs. Gen 4 RSA : Does It Affect Accuracy ?

I don't see how it could as long as the Gen 3 spring locks it in battery, well enough (aka 'lock up'). It's possible the dual spring could cause a little more muzzle dive when the slide returns to battery, after a shot, so it may make accuracy worse...from an off hand perspective. On the flip side, it should keep the speed of the slide lower, to the bottoming stage of the cycle (slide all the way to the rear), thus reducing muzzle flip and letting you get back on target, quicker...one trade off for another. As far as mechanical accuracy, I do not see how it would help other than keeping the slide locked up a tic longer, but that would be something you'd have to test. I've no clue what the progression of each RSA is at the beginning of a cycle.

If properly sprung and operating as designed, no.

Bullet is gone before RSA does a thing.

no

it adds a little extra weight and that could make the gun feel less likely to move during firing

kind of like the recoil spring with steel guide rod effect

No.