or would it be better invested in the sneak skill o.0 ?

or should I get the intense flames perk and use the last 3 perks on smithing which i dont even do except when making jewlery to enchant .-.

only three schools remain in magic enchnating illusion and alchemy but enchanting is level 92 the other two schools havent been touched yet (im horrible making potion i made some health potions but every time i used them sounded like iwas being electricuted so must of been some hidden negative effects on it...)

No Sneak skills mask the sound of spellcasting. If you're a sneaky mage or mage-rogue hybrid, then Quiet Casting is worth it for dealing with multiple enemies.

I'm niether just pure out mage unsure on what to spend perk points on any more XD once I get the dual enchanting perk every level from now on just what do I use it on ....

So this Quiet Casting perk makes "sneak attacks" with magic possible?

Is there any bonus like with melee weapons & bows though?

train the skill in those class and sneak

magic make light and sound unlike blades and arrows

Almost all magic spells force you to Speak the spell, which makes a very loud noise and even with 100 sneak in pure darkness the bad guys will find you and hit you.

With quiet casting ALL spells are now cast without making a sound and thus you can recast invis and never been seen, or launch a fireball while sneaking and stay hidden until they start looking for the source of the fireball. (it does not allow magic spells to do backstab damage though).

Of all the perks in the illusion tree Quiet casting is the best for any mage that wants to sneak.