You mention club linesman, did you work with ARs or was it primarily by yourself?
I've lined to a referee several times, but never worked with neutral assistants. The vast majority of my games are done alone.
The diagonal system of control is intriguing to me considering that the soccer pitch is larger than a football field and you have just as many players.
Different game. As a rule of thumb, there will be relevant action occuring in (at most) three parts of the pitch at any one time.
1). As a unified whole: the ball, the area surrounding it, and the area where the ball has just been, where there is
always relevant action (even if it's gone out of play and over the hills and far away, there's timekeeping concerns).
2). The area where the ball is about to go, especially the drop zone after a high ball or cross.
3). The offside lines.
It's impossible for the referee to give offside accurately (there's ways and means of fudging it when working alone and a lot of teams who are used to it have been trained never to expect an offside decision and to stay goalside of the attackers at all times), so you put an official on each offside line, and suddenly you've got enough pairs of eyes to see everything.
It's funny. I've lost count of the number of times I've explained this sort of thing to soccer fans, except this time I'm doing it backwards (because I'm usually explaining how in football you can easily have seven or more areas of the field that need watching at once).