I apologize for a rather long explanation but it is necessary to understand the issue.
To begin, we know that the most reliable way to buy the ticket is directly from airline. But this is not always possible, and sometimes we need to use travel agents.
Now there seem to be two kinds of online travel agents:
One which issues the ticket immediately upon purchase. Those include mostly the ones in Priceline group: Expedia, Orbitz, Booking.com and so on. When you purchase a ticket from them, it is issued and confirmed immediately.
However there is a second group of online travel agents - such as Travel2Be, Flyfar, GotoGate etc. With them once you click "purchase" you just sent a request to someone to buy a ticket for you. The actual ticket purchase happens later, and in a few hours you either receive the ticket, or a quite lame response ("We have some good news - your credit card has not been charged! But sorry, your ticket could not be issued" or something like that)
Both groups work fine when you book well in advance or a non-popular route (although I had bad experience with some of those agents). However this difference becomes critical when you're buying a ticket for a flight where the availability is diminishing fast. What happens in this case is different between those:
Orbitz etc show you a good price for a flight. In some cases as soon as you click to buy it, you get the "Oops, this flight now costs $2000 more, still wanna buy it?". However once you purchase a flight, it is purchased.
Travel2Be etc show you a good price for a flight and accepts the payment. Then you will get the above message 4-12 hours later in email.
Obviously the second scenario is much worse, because you just lost valuable time, which you could have used to find alternatives more quickly, before they also sell out.
Thus my question is:
Is there a reliable way to find out fast whether a specific online travel agent issues the confirmed ticket immediately (like Orbitz/Expedia), or works on an order taking basis (like Travel2be/gotogate)?