I just have a single on/off valve for both hot and cold water.

You may want a separate on/off valve for each. I prefer the single.

No need for a separate feed for the dryer. Like you said, just use a Y fitting to branch off the cold water for the dryer.

If you go separate, opt for the quarter turn on/off instead of the multi-turn valve.

I've never used the shut off valves ever except when I am swapping a machine - which is literally like maybe in a decade.

I don't plan to use a washing outlet box.....going to build a tiled niche, with valves and outlet for drain. The shut-offs will be standard 1/2 ball valve accessible in a access panel in the room, out of sight, out of mind. Why tile.....while a outlet box will do the job, it just looks so pedestrian....even if you never see it.

I think I'm erring on a 2nd cold feed. Not sure but to my eyes it will be -cleaner- than a Y

Here's a pic of my laundry area in my basement.

You can see my Y connection behind the gray drain line.