Castrating does NOT help with behaviour in guinea pigs. It’s a myth that it does, it doesn’t have the same effect as with cats and dogs.
I adopted 4 boys and found that in themselves they made 2 groups, ie. two got on with each other better than the others. And the only way to help them leave a happy life was to separate them into two groups so they didn’t have the stress of fighting for dominance.
It is very rare that males in a group of 3 or more work out, as it’s not natural for them to live like that, as in the wild you usually have single males, this is why pairs have to be so carefully selected during the bonding process.
Hope that helps.