A question about shop layout and prefab shops.

Hello Woodworkers, I am looking for a bit of advice on two things – and I know this community can be quite opinionated. :-)

1. I am looking for shop layout software. I’ve tried a few websites like homestyler and floorplanner (free versions) – and attempted to use sketchup. I am curious what most people use / what’s the easiest and geared towards shop tools. My shop is a maze to walk through.

2. I have a 3 car garage – 2/3s of it are taken up by storage, work out equipment and stuff that the wife says’ she still wants (and will use one day ~right …), gardening, patio, etc. The rest of the garage is shop tools that I keep accumulating (which I know is a problem for most here).

We are looking to build a shop in our back yard (it’s a mildly sloped hill w/ a lot of alder trees). I am looking to keep things fairly within a reasonable budget. I am looking for experiences from people that have built shops before / built pre-fab metal sheds and laid slab / etc.

I am in the Seattle area – so it’s quite wet here =/ - and I’ve forgotten what the sun looks like. I am going back and fourth with the metal shops since I'd like to avoid rust / humidity inside.

Any advice / or experience that can be shared would be greatly appreciated.

Thanks