RC papers will buckle, craze, and delaminate somewhere around 220F. But 190F is not a problem.
Badly applied canvas coating will sort of melt at rather modest temperatures. Worst case is when somebody has piled on way to many coats trying to fix this or that coating problem. But good coatings will stand up to at least 180F for at least the time needed for a typical vacuum heat cycle using Fusion 4000 or similar adhesive-only tissues.
Other than that, most inkjet media will stand up to at least 190F for extended periods of time.
Clamp down on a reject print for about 20 minutes at a little more than the temperature you think you'll need, nothin' better than an actual test. I have done this a few times and never saw any problem that I could identify.
You mentioned that you are using a vacuum heat press so moisture will not be a problem for you. However, for the record, anybody dry mounting with an old fashioned clamping press definitely will want to press the print + backing - tissue for a couple minutes to drive out the moisture prior to the actual mounting procedure. Nothing compromises dry mounting like moisture in the media, and failing to drive out moisture is the biggest mistake rooky dry mounters make.
And of course, develop a keen eye and sensitive fingers to detect the tiniest mote of junk between backing, tissue, and art. Nothing in this Universe more ugly than a bump on a dry mounted inkjet print, especially glossy ones. That's one of the reasons I don't dry mount anymore, the other ones are heat, time, and generally excessive fussiness.
