Mac slow printing - spooling problems?

I have a new HP Laserprinter MFP M283fdw and when printing a 50mb document from Pages via my MacBook or iMac it takes forever (5-7 mins) before it starts printing. Files under 500kb are not a problem - anything over takes progressively longer to print.

My HP OfficeJet Pro 8620 printed everything I threw at it immediately - so why is the new laser printer so slow to start on the bigger print jobs? Just spent a couple of hours with HP support at tried everything including using Wi-fi Direct that circumvents the router and lets you print directly to the printer. All to no avail.

Somehow I don't think returning and exchanging the printer will make a difference - I have strong feeling that the problem lies in the way the MacBook and iMac send the data and the HP Laser Jet receives it. I think it's called buffering or spooling.

Can anyone offer a perspective on this issue?

Thanks :-)