OK - gonna have to read up on synthetics +++
clear that once short in crossed spreads the risks can get ugly
was thinking: practice first with long only volatility plays (guts / straddle / strangle)
Your risk on the out vs. inside in ATM structures with (any) time to expiration is not assignment. Your risk to gamma is an OOM larger. It is best-practice to trade the outside strangle due to microstructure. It's easier to move in and out of the trade and the NBBO will be tighter. Always choose the OTM structure when possible.
An example of a complex vertical and synthetic (OTM) equivalent.
XYZ at 1200.
Asym-put fly (NATURAL) = L2 1000P; S3 1200P; L1 1600P. Traded as a spread as all puts.
Asym-fly (SYNTHETIC) = L2 1000P; S2 1200P; S1 1200C; L1 1600C. Trade the above put fly as a synthetic (COMBO) in puts and calls. Truly, it's not a huge deal. You're not going to earn (much) more by trading the synthetic, but everyone trading complex instruments should have a foundation in synthetics and arbitrage.
The two positions are arb-equivalent. They have the same payoff. You'll receive a better fill in trading the combo. The natural has a 400 point ITM leg. The synthetic is trading an ATM call vert (the synthetic put spread).
The call vert in bold is equivalent to the 1x1 1200/1600 ITM put vert in italics. Again, constrained by the box arbitrage and well, algebra. You can involve shares in the (CONVERSION MKT) and the shares simply offset.