wood type for framing?

Who is saying to glue the joints? Because I have heard people that have been rebuilding trailers for years say that they do not glue the joints.

Kind of what I'm trying to find out. If it's a bad idea I'd like to know beforehand!

It sounded as if he (video) was talking of putting glue into the holes. Did I interpret that correctly?  I have been gluing the contact areas prior to tightening the screws.  Maybe it doesn't really matter either way on the glue.  I'm interested in hearing other opinions.  Glue or no glue - enjoy the rebuilds. 

Mine had all the panels glued to the framing and it was so strong I ruined many panels and had to sand off glue residue on the framing I reused. I also glued my panels back on because my wall staples were pretty floppy in places so it helped hold it all together

No glue on framing, but on cabinet face frames etc good. Kreg jig good for cabinets too but vintage trailers didn't use screws in framing joints, only fastening walls to cabinets with some higher quality trailers. Staples were the common fastener of the day, and although irritating when disassembling, they make quick work for assembly, and don't leave hidden heads like screws do, a real pain when attaching subsequent layers (skin, and J or cap rails) which inevitability are blocked by those screw heads.
I know it's tempting to want to build better than original, and I was guilty of that desire when I first started on Scotty because I came from boat yards, but trailer stresses are different, and in my opinion, when dealing with 50+ year old campers, their most common reason for failure was not necessarily poor construction, although they were for the most part quickly and cheaply built, but is because owners never replaced putty tape, never pulled windows or lights off to see that they were soundly in place, etc.etc. Scotty was probably one of the most cheaply built of it's generation but although the rot was extensive, the only rot that wasn't attributed to putty tape failure was what non-plywood wall construction would be called skirting, and that could be because none of the original lowest wood surfaces was waterproofed. Scotty is 50 years old and although was crusty and mouse-poop filled, it was still standing, and as built in '69 it's life expectancy probably was never even considered, and the people on the assembly lines probably only cared about getting through to the next paycheck, not 50 years later, who am I to argue with their techniques.
So, in my unasked for opinion, don't try too hard to over engineer your project. Study how your unit was put together (except for maybe adding more front and rear framing (I did))and try to replicate original methods.
Probably my most long winded reply, might have to take a nap now.

post script. Could be the only reason Scotty might last another 50, er maybe 20 years is because, should I live so long, I'm a plodder and it could take that long to finish.

I agree with the above thought, any camper that survived 50+ years doesn't need too many design improvements. But a little glue in key places shouldn't be a big deal. Dan touches on a good point, once glued (for better or worse) it won't ever come apart in a surgical way again. If you have a small accident, the camper may not be repairable without hacking it apart with a saws-all.

A word on oak... my understanding is that if an area is expected to get damp, don't use red oak, it's pourus and will absorb the water. White oak is the preferred wood.

Unfortunately, red oak is the easiest to find, white is difficult.