Stock Glocks are just fine and I shoot them extremely well. However IMO the great thing about the Glock is that is easy to literally "hand fit" the weapon to the shooter. Oddly enough people do all kinds of things to expensive 1911's to "enhance" performance, but some people think that doing that to a inexpensive Glock is silly. It actually makes more sense to do it on a Glock as it is much easier and much cheaper to perform on a Glock than say a 1911 AND the results can be literally night and day. It makes less sense to not optimize a Glock to the shooter if that is what they desire. I don't suggest people automatically do such modifications but rather suggest they learn the pistol as stock and it will give them a better idea of what modifications that they may like. I did not assume that you were still learning it, but rather have informed reasons for wanting the changes.
For myself I have smaller hands, which is why the Gen4's were perfect. Larger mag release button which was easier to get to and I didn't need to alter my grip on a reload. For an extended type with the same button profile go with the Vickers in a Gen 3 or with the factory extended I tend to radius the edge. We were doing this long before the Vickers and it is easy to do, but the Vickers is done already. I too like to purchase parts from Brownells as I do have an account and that does help. Anyone who qualifies, should look into an account with Brownells. Stock parts I tend to come by from the factory.
@GS, going from a 10lb trigger pull to a 3.75lb pull was not just the connector, but also ditching the NY trigger spring for a standard spring which IMO is a good thing.
As for the Glock knuckle, if a shooter does not have that issue, either the shooter is probably not optimizing their grip, not shooting a high volume of rounds, or has leather, no, stone for hands. If you do suffer from Glock knuckle, hand fitting the Glock is a lot cheaper and painless than undercutting a 1911.
As for the trigger, stock is not bad but it just takes a good bit of rounds to smooth them out and overtravel will be what it is when left as stock. Good trigger work from a reputable person can optimize all of this instantly when performed correct. I do triggers from leaving it at the stock 5.5lbs pull to about 4lbs on a defensive type of pistol, but the feel and travel is much better. For range or competition I can go as low as about 1.5lbs, but just because I can, doesn't mean that is my preference. The lowest pull I actually prefer is right at about 3lbs for a range or competition pistol. If you pulled any of my Glock triggers, besides the two that must remain stock, there would be no going back.