I just had to cancel a QR trip booked on Trip.com. They refunded the amount due within days, and my insurer will pick up the difference. I can't imagine that QR would have been any more efficient if I had booked with them.

I used that OTA because they offered a fare around £70 lower than QR's. I do that routinely where the fare difference is significant, and I've used any number of different OTAs. Buying directly from QR triggers a 3% cash-back at the moment, so i factor that into my decision, as well as the ability to see what fare-class (RBD) I am buying. And, indeed, I've just bought a ticket from QR's website for those very reasons.

Hand on heart (and touch wood!) I've never received lesser treatment flying QR on a third-part ticket, but there again my travel is usually fixed. Where QR has disrupted my plans they have looked after me regardless of the mechanic of ticket purchase. When (mid-trip) i contemplated changing my return date the airline simply applied the fare rules - and scared me away from the idea !.

The long and the short of it is I have never had to deal with the OTA in any way but the most straightforward. I've no doubt they would be nightmares to deal with if i wanted to do something like invoke a Qsuite-change benefit: but as I don't give a tinkers about Qsuites, I'm immune from that drama.