And do the potion and draught have to have the same value?

Ah sorry I didn't think that sentence through. You drink a potion of the healer followed by a draught of the healer.

I know Necromage is a pain, but once figured out, it is definitely worth the reward!

Ok so I'd be taking a +20potion followed by a +20 draught and then equip 2 items worth 20 stamina each to trigger this glitch?

A potion of the healer has a value of +20 resto, while a draught has +30 resto.

So by drinking the potion first and then the draught you get something like Fortify Restoration by 36%, you then equip the two items with enchantments of 20 stamina to get infinite stamina.

The second potion overwrites the first but is modified by it so you end up with a 30% fortify restoration effect boosted by 20%. The maths is 0.3+(0.3*0.2)=0.36 so 36%.

So my math was right 

Yep. I have infinite stamina now. Just ran from Solitude to White run. Left my slow ass follower in the dust. 

That's great. I was using it, but ended up upgrading to "Philter, Draught with +20." to free up one of the equipment slots. 

If I transform into a wereworlf or vampire lord, will the effect be undone?