Yes, all that stunted growth or changing their personality or humping and marking those are all myths. And the things like lesser chance of cancer - well, duh, if you don't have balls, you can't get cancer of the balls. But, the chances of them getting cancer with their balls intact is not significantly higher that it would offset the risks of the health risk of the neutering/spaying process itself when you're dealing with the breathing issues/allergies/general health condition of bulldogs that is exarcerbated during surgery.
And the dog behavior is more a product of his training and natural personality than his neutering or lack thereof. But, it is true that an intact male is more territorial than an altered male. Also, an intact female has the natural tendency of wanting to roam when in heat. Of course, if you're the alpha "dog", these types of behavior issues can be avoided by proper training.
Okay, so, that said, why neuter and when to neuter? You neuter simply for the fact that you don't want to have even a 0.0001% chance of getting unwanted babies. That's it. Now, spaying is a different matter. The procedure is more invasive but not doing the procedure is also a lot more responsibility. A girl in heat requires a lot more maintenance so there's more added incentive besides just eliminating the even miniscule chance of having unwanted babies.
When to neuter... 6 months old is standard - both males and females. English Bulldogs mature later than most dog breeds so you might have balls that hasn't dropped yet so you might have to wait a while for the males. No, neutering/spaying at 6 months old won't make the dog smaller. No, it won't make the dog cuter. No, it won't change his personality.
That said... I have 2 intact males and a spayed female (spayed before we got her). And here's some mythbuster things about my 3 dogs - the spayed female is the one that humps. By the way, humping is an act of dominance - so even females who want to establish dominance will hump, altered or not. The one intact male has terrible separation anxiety issues so he would mark everywhere when left alone. He doesn't mark at all when we're around. The other intact male neither humps nor marks. He's the super omega dog.
So then we had a German Shepherd mix that I babysat for a while. He's intact too. The first time he walked in the house, he got in a fight with my intact male bulldog who is the omega dog that got territorial. I'm not the alpha in my household. I'm a wimp, actually. My husband, who is the alpha dog was out. So, I had to separate the dogs in separate sides of the house. So, the next morning, my husband took the dogs out and there was not a single bark or growl from both dogs. He leaves the house and the dogs remained behaved and played together like old buddies.
Okay, before my husband and I got married, he had 2 intact male dobermans. Now, if you know dobermans, they are quite the protective breed. Those dogs got in a fight a few times when they hit puberty so much so that we had to spend $800 on stitches for both dogs! But, with my husband's consistent training, he was able to get those dogs to play nice with each other so that when we got married, those two dogs were the sweetest dogs even with me, the wimp, taking care of them.
Now, my friend has 4 dobermans, 1 pitbull and 1 boxer. 2 males 4 females all altered. She spent over $1,000 on stitches when they ended up fighting too but she established pack hierarchy soon enough and everybody except the boxer gets along great. The boxer, though, had more psychological issues that she had to remain separated from the rest. Now, this shows that it doesn't matter if the dogs are altered or not - their personalities does not change. An aggressive dog will be aggressive, an omega dog will be omega. A dog with psych problems will still have psych problems.
So, if I ever make one teeny bitty mistake and my intact dogs get out and impregnate another dog (my neighbor has 2 intact female boxers), there is nobody to blame but me and I need to be scourged for it.
And that's my thoughts on the matter.