Yamaha's FS prefix indicates a Concert body. Also available as a cutaway. Storia is also a Concert body.

If you're looking at Yamaha, here are their acoustic body size prefixes.

FG = "Traditional Western" body. A Dreadnought.

CPX = Medium Jumbo

APX = Slimline Concert cutaway. This is what I have and my favourite acoustic of my four. Pick of the bunch. Lubbly jubbly if of average build and you want a fast acoustic neck and body comfort.

APXT2 = scaled down Concert body 3/4 size of the APX. Travel guitar or for tiny people.

CSF = Parlor, a small body. If you're looking for a compact package with big sound this might do. Yamaha's CSF promo. Check it out. I suspect it might be what you're looking for. Edit: Another high signal to noise ratio review & demo here with other models placed alongside e.g. APX600, CPX permitting a visual relative size comparison.

manXcat

P.S. Chair wise, no real suggestion other that what I use most of the time works for this old body. No back suport with it though other than what it invites through good spinal posture. My On Stage KT7800+ keyboard bench. I bought it for use with my Yamaha keyboard & stand, but I favour it for use with guitar over my guitar stool. Deep memory foam for comfort, and [u]importantly[/u] adjustable height so my legs rest squarely and firmly on floor when seated playing guitar.