There are a fair amount of factors that need to be considered, which is why you are getting multiple, and different answers.
Regarding fueling hardware, our standard stage 2 LPFP supports ~550 whp on 100% e85. The HPFP however only supports ~420-430ish whp on full e85. If you wish to achieve the most power, and utilize full e85, the HPFP needs to be supplemented. It is this very reason some choose to run blends, e30, e40, e50 and so on. PI will open up more power potential, that being said feeding the 6 additional injectors in the PI rail, does put some added strain on the LPFP (it's really a give & take relationship here). To answer your question, yes, PI + stage 2 will open up more headroom. The limiting factor in your fueling will no longer be the High pressure side, but now the LPFP.
It really comes down to a few things, power goals, and budget.