Hey I'm 38, play with my little brother (in his 20's) and have a 7year old who is desperate to be 14 to come play with daddy.
Hops work like this.
There is a hole in the barrel with a rubber cover on it. It has a nub, small bit of rubber/plastic resting on the hole. When you adjust your hop you press the nub down giving a little bulge in the barrel. When the bb gets sucked into the barrel and pushed by the piston/plunger thing (forgot name), the little bulge makes it spin backwards. This spinning makes it go further. However too much spin and it goes skywards.
So to get more range you start with the hop off, wound down, then gradually turn it up till it just starts to fly up instead of flat, then turn it down a titichy bit. You also want to make sure that you shoot a few rounds before play to soften it up again once the gun has been sat for a while. (or that may be me)
Basically yes, the hop gives you much more distance than not having a hop.
I have a RS type 97b who has to have the hop at 7/10 to be any good
I have an src that needs to be at about a 5/10
I have a jg beta spetz that needs to be at 3/10
each have different hop set ups so need more or less hop applied
I get good groupings with the RS and SRC at 40m and good groupings with the spetz at 30m, but the spetz is more of an indoor gun tbh.
M14's are pretty good at range end of story.
His g36 can be improved by sticking a new hop rubber and hop nub in the gun (about £12-15 of upgrades), but depends upon what make of gun it is. If he does want cracking range then p90's are supposed to be good as well
He will probably not get the range you do with a hop rubber and nub change, but he will be close.