If OP holds it to expiration, the only thing that matters is where the underlying ends up. If OP plans to exit prior to expiration, then volatility matters. Not just volatility but skew, term structure and the rest. OP can model the behavior of that particular butterfly by playing with IV, skew and term structure in BSM instead of asking us.
"so if i have a butterfly a spike in IV will kill it to the downside" Depends how wide it its and how close the "guts" are to the ATM. The wider the fly and the closer the middle is to the ATM pt, the more IV risk (negative) you have.
Homework for your BSM modeling: 1. Change butterfly body width 2. Change IV, e.g. double and half 3. Change skew, smirk, negative skew.. 4. Change term structure, time. You will find your own answer depending on all of the above. Since BSM is just an approximation, you will only get the general sense of how things move.
Extra credit: 1. When you buy two adjacent butterflies, what do you get? 2. At what point on the IV curve does a long butterfly position go from being short premium to long premium? 3. If you add all the same width butterflies on the smile what do they equal?
Good question. Of course it depends which delta-wings you buy, but trading iron fly's when the VIX is higher makes trading these more profitable in my account. My average daily P/L was almost 4 times as large (which makes sense; VIX>20=larger St.Dev of P/L. My POP also increases when trading fly's with a higher VIX. Flys depend on your pin strike (directional/non-directional bias), if your playing ATM gamma curvature or choosing to predict pin binary events... also focus on your awareness of which wings will work the position best. Dabble with the prices and find the best R:R because fly's offer huge results if implemented correctly within the implied space.
Is there a particular name for this? I'm just assuming its two fly's along the vol-strip. Usually when a trader does this position he's playing for the expected move for both put and the call fly.