Just some random thoughts on these issues:
Velvet Fine Art has the highest D-max of any mat paper available (it is the same paper but not the same coating as Somerset Velvet (test them side by side with or without a densitometer, it is obvious). Crane Museo Max is second for d-max (a paper I helped beta test). The Hanemule papers have a relatively low d-max. If you mix traditional silver prints with archival pigment ink in exhibits, as I do, D-max is very important. otherwise not quite so much. Tonality wise Enhanced mat is a good proofing paper for both.
I load 13x19 Velvet Fine Art from the front (not the tray) of a 4000 2 or 3 times a week and have for a couple of years. Line up the paper (pushed over to the right) with the front top edge of the front of the printer. It works fine.
For larger prints I use the CMM. It has very similar characteristics as Velvet, but on a warmer base and less texture (under glass the texture all but goes away anyway). CMM is warmer because it has no optical brighteners at all. It is the whitest paper you can get without optical brighteners. Any paper whiter will yellow in a relatively short time anyway if exposed to light, because OB's yellow.