I signed up for the Westpac World Mastercard despite some unanswered questions. No regrets. It comes with the full "unlimited visits" version of Priority Pass. I've used it six times in a couple of months already.

Yes, the Priority Pass does come with the condition that if lounges are full, they can decline entry. However, this is the same for Diners Club which I was using before. In around 25 years of Diners usage, I was only declined twice - and I think there were time bands where usage wasn't permitted which I didn't take notice of.