AJ
Contributor
I bought a rebreather last year (JJ-CCR) and did training with IANTD. I did not have formal tech training nor on using stages except for a workshop or two and some diving I did on my own. Knowing what I know now, I must conclude that having some formal training on how to handle stages helps a lot. Knowing how to handle stages blind folded flattens the learning curve. Learning to a ccr is complex, anything makes it easier is very welcome.Having ANDP will help prepare you for CCR training. Not having it will almost certainly result in the more restricted pass, e.g. 30m/100ft.
Although I did struggle more than my training buddy (full trimix instructor), I managed and learned how to deal with the complexity of ccr diving. I'am now normoxic certified, planning on full trimix and cave (cavern first, then full cave) in the coming two years. So it can be done with just AOW (and GUE Fundamentals Tech).
My advice is: take your time and do the AN/DP. It will help you whatever you're going to do next.