1. I used EF's search for A inventory when I did this back in 2019. I was only checking P this time (because I was lucky even to get that on BOS-HNL). But transfers are instant, and I would 100% recommend that you get the reservation booked, call the agent, and then just do the transfer right then online while you have the agent on the phone. It takes less than a minute and the agent will wait for you. Also, make sure you book the economy tickets through Hawaiian and not through a travel portal like Amex Travel or Capital One Travel... I made the mistake of booking through Capital One first to get the $300 Venture X credit, but Hawaiian won't touch that reservation (and neither would Capital One went I went to cancel it, so we had to do a three-way call that took 90 minutes just to do a free within-24-hours cancel and refund!).

2. Yes, definitely if you are on the same PNR you can use your miles for yourself and others. If you want miles to come from different accounts, you have to split the PNR. Can't say whether you can use your miles to upgrade someone on a different PNR... maybe someone here knows. I would not rely on what a phone agent says, because they might put it in the system but it could still be rejected later. You aren't home free until the ticket is reissued and the reissued ticket is emailed to you.