I do a ton of long distance driving for weeks and months at a time, so have been poking around a lot and asking a lot of questions from users. The Grdian DEFENDR+ GRD-A55 and GPS adapter seems to be a fav for a lot of people and kept coming up with great reviews, so that's what I'm going to get for dash cam. Hadn't really thought about a 2 channel, but like the idea.
Already bought an AUTO-VOX M1 Rearview Backup Camera & Monitor on Amazon ($49.99), mainly for those last couple inches backing up when hitching the trailer, but am going to hook it up as always hot, though with an on-off switch, instead of just coming on when I go into reverse.
That way I can use it as general back-of-the-vehicle cam when I'm parked and in the van (I have no windows in back), or while going down the road and want to check on the trailer. Would be nice if I could hook it up to the Grdian Defendr storage, but I doubt that's possible.