Is PMax worth it when the conversion is an enquiry rather than a purchase?

It works without a feed, and your second worry is the real one - it is not a worry, it is a certainty unless you address it. On the feed: asset groups do the job a feed would. You're giving up the automatic generation of a listing per product, which you do not have anyway. Plenty of lead-gen accounts run PMax perfectly well on asset groups alone. On optimising toward cheap enquiries: yes, it will, because that's precisely what you asked for. Optimising to a form fill buys you form fills, and the cheapest form fills in hospitality are the ones from people who were never going to book. This is not a PMax problem, it is true of every automated bidding strategy - PMax just has more freedom to act on it, so you see it faster and harder. The fix is to make the conversion you optimise toward resemble the outcome you want: Send back the booking, not the enquiry. If your system can report which enquiries became stays, import that as a conversion. It's the single highest-value thing you can do here. Failing that, use values rather than counts. An enquiry from the high-value segment is worth more than one from the cheap one - if you can approximate that at the point of the form, do. Without one of those two, I would not run PMax on an enquiry conversion. With either of them, it works fine.