I'm not the teacher, school got raided today- see Oaksterdam University Raided by Feds- I'm just throwing some techniques out there that have worked for me.
First, the limit to the number of side shoots has to do more with space, light and available nutrients than it does with an exact number.
Second, the plan I follow is to top the plant when it's only 6" tall or so, and strip all but the four best side branches. This will start the plant on its way to being a bush rather than a pine tree. Once those side shoots get long enough- and that's a matter for personal preference, strain, growzone size, etc etc- top them, too.
You do not want to top too much or you end up with a plant that's so bushy it shades itself.
The aim is to end up with a plant that between the topping and either tying down or SCRoG is roughly flat across the top. The commonly accepted term for cleaning up stems too low to get good light is called 'lollipopping' and I recommend it.
Here's a guy who has the general idea down to a science;
https://www.thcfarmer.com/community/threads/larry-og-vs-tahoe-og-in-dual-monster-plant-system.46731/. Scope out his pics, they'll tell you what you need to know.
His techniques differ from mine, but the desired end result is the same, and boy, does he have results!
I guess when people think 'topping', they think of doing it as an afterthought, well after the plant has established its structure- by which time it's too late to do much about it! The heart of my approach is to make that first top early, so the whole plant grows out from it.
