Suburban sets might typically be about five PRs plus a van, of course. First time I ever travelled on the Cobh line in the early 70s, the train was (I think) two PRs, a laminate and a 4-wheeled tin van. But many photos show 4 or 5, and also in Dublin 5 or even 6 would be commonplace on suburban runs - but - mixed in with laminates. Rarely would a train be ALL PRs. Naturally, no matter what coaches you use, a genny van of some sort needs to be in the consist.
The snack cars were not in green, as they were introduced after that livery had been replaced. Only black'n'tan.
PRs on intercity trains were a complete mixed bag. I doubt if an intercity train was ever composed of nothing BUT PRs - I certainly never saw one and am unaware of any pictures showing them. Theoretically, of course, it's possible. The various types of laminates outnumbered the PRs, and there were of course Cravens in the mix too, after 1963. Thus, any typical main limne train could have had several Cravens, several PRs, and several laminates - and up to the early 70s, one of the last few Bredins.
As to numbers of vehicles (of whatever type) on main line trains, this could vary from maybe 5 or 6 to 10 or 12; again, with genny vans.
The longest train I think I ever remember was a Cork departure which I think was about 10:30 out of Heuston. It tended to load well, and I saw it once passing Port Laoise with 10 or 11 bogies (a mixture of this and that, of course) and a van on each end. My friend Barry Carse once saw thirteen bogies and a van on (I think) a GAA special.
Loads of nine on Cork and Belfast services was commonplace, but again, of those nine, maybe only two were PRs.
Pretty much any type!