Concur on compressor outside. Takes up a lot of space, makes a lot of noise. Just poured a small concrete slab with studs in it, made a lean-to type overhang off the back of the garage, slapped some exterior sheathing on it, done. Draining the tank you have to go outside, but valve for air is inside. With no plumbing leaks, never need to worry about turning it on/off. If you have the money, they make automatic tank drains, but I have no idea how well they work in the long run, and IIRC, they are pretty pricey.
On the bench, I used 1/4" plate as a top for it, countersunk bolt heads so nothing to snag on. 1" edge overhang for the steel (3/4" plywood underneath) so you can really clamp things well. Made it L shaped because there is a stub wall so it was convenenient, plus putting the vise on an accessible corner makes a lot of sense. 30" sounds about right, I've got an arc welder on a stand, two 350's, a 205, and a 465 underneath it, plus various other parts, and they are never in the way. Tabletop is fairly high, as I didn't want to be bent over all the time while working. High enough that a motor on rolling cradle (not engine stand) fits under it.
I tried to keep everything yard related in the house garage. Doesn't ever work out that way, the mowers take up a LOT of space no matter where they are. I hung pretty much all the yard tools I could, which frees up floor space. Same deal in the garage, the overhead space is often wasted, I got my hands on a ton of pegboard, so coated the walls in that as much I could. Pegboard isn't real strong, won't hold a ton of weight, but its adaptable for just about anything that isn't overly heavy, and the hanger pieces are pretty cheap. Also a good way to hang spare parts.
Bottom section of the walls are 4x8 sheets of painted chipboard (with a tiny space between it and the floor to prevent rot) as I figured drywall would get destroyed quickly. Easy to remove and install if you need to access wiring, or whatever.
I have a fair number of heavier duty shelf units that are ~6' tall and fairly narrow, that helps for the heavy stuff or organizing smaller items, while still keeping them somewhat out of the way.
Tons and tons of outlets. You will never have enough. The one you need right at that moment will always be covered.
Lighting was a PITA. I got my hands on 4 bulb fixtures for free, but only about half the bulbs work in each. Put three fixtures per bay, right down the middle. Rolling up the door covers one of them, which is problematic. Probably better to be situated between the bays, and either one on a switch, or on at all times, over the workbench. Lighting behind you doesn't work well. Each bay is on a separate light switch, since you don't always need every bay lit up, and if lighting is adequate, you don't need all the other ones on. I also installed a "lit" light switch for the first light bay, so when reaching in the door when it's dark out, you know where the switches are.
I laid down plywood on the rafters to store fairly light stuff that I won't need to access often.
All the stuff that rolls (mig welder, engine hoist, horizontal band saw, tool chest, etc) ideally sits between the bays when not in use, that depends what vehicle is in there, how much clearance there is with door(s) open, etc. Never enough space, but I have a hard time keeping things (projects) from creeping in there.
