Question 1: How consistently are you able to hit the ding with your current driver?
If you're hitting the ding more often than not, the G20 is going to be better because it is more precise. Think of precision as the size of a circle around where you're aiming. The more dots of precision, the smaller that circle will be - thus, your shot will be closer to where you've aimed. The slower meter will help with hitting the ding. Add in something like the Callaway balls and your chance at getting the ding is even higher.
Forgiveness is how close to that circle of precision the ball will be on a mishit. Higher forgiveness means you will get closer to your aiming point with a mishit, BUT - the circle that the ball will land in is bigger, so even on a ding, there's a wider area the ball may land.
The higher loft on the G20 is also important - the wind will have more affect on the flight of the ball. The trade off is stopping power with the higher ball flight (not as important with a driver, but can help when considering the irons).
I know you're aware that suggestions are based on distance and this is for good reason - the tees move back when you reach Master and even though it's "only" 18 yards, it is a HUGE difference between hitting a 3i into a green vs. being able to hit a 5i. I tried to carry the K15s into Master and struggled because it was so hard to get close with long irons.
I have the G20 (I bought the entire set when I got to that level) and I have no regrets at all. They take some time to get used to because of the difference in loft, but once you figure them out, they're incredible clubs.
Hope this helps!