Q:
Illusion Generation
You have 3 illusions out. You shatter. At this point, your little illusion dots will still be filled, but the shattered illusions no longer count. You can rapidly spawn 3 more before your first set reach their target and shatter.
No to first question.
Spam forth and worry not.
Once you hit the shatter button, they no longer count towards your 3 illusion limit. So if you hit Mind Wrack for example, you can immediately summon 3 more clones while the old 3 run toward the enemy.
In theory, you can have up to 15 clones up at a time, assuming you summon 3 clones, shatter, summon 3 clones, shatter, summon 3 clones, shatter, summon 3 clones, shatter, summon 3 clones, all while the other guy runs away to avoid the clones actually shattering. Of course that’s ridiculous lol, but I’ve seen 9 at once before, it’s definitely possible.
Tarnished Coast [Crit]
If you reflect the scepter auto attack, you can go over the 3 clone limit. I know this works for other classes. Idk if the would count for mesmer illusions or not or if they fixed this.