A:
I found the capacity of the 7/8 be be pretty large. Some 'large arbor' style reels can be pretty skimpy re: room on the spool. Not so here. I set up 3 spools with 7 Wts - all full length WF - a floater, a sink-tip and a full sinker. I got plenty of backing on each spool. Way more than I'll ever use. I'm sort of the mind set that if a fish gets out 200 or more yards from me while hooked - I'm likely not going to land it anyhow.
That said - you will get more backing with a 7 WT than with an 8 WT. Ditto for 8 WT vs. 9 WT.
I think you would have plenty of room for back for trout fishing. The size and weight of the reel would match well with most 8/9 WT rods, I think.
I don't know that I would use this reel for salmon, steelhead or bones . . . but, it might be just fine.
I am hoping to catch some trout in MT this summer to tax it a bit. But, I'm not holding out for any 15#'ers.