Regarding the F last vs GG06 last they are completely different. Both are round but the F is sleeker with a beautiful raised profile and look very elegant. The 06 is much wider and flat. The shoes I had on the 06 last gave me the weird impression that the front of the shoes (toe area) had no correlation with all the rest. I can't help much regarding the waist and fit, I was stupid enough to purchase 3 G&G 06 but only did wear one of those for one day and they fit well, but I just couldn't look at them and sold them. IMO if you are going to G&G, go with the sleeker lasts except maybe for boots.
I know my shoe vocabulary sucks but I hope you get the idea.