This response may not make the planning any easier, but...
The main space is 24' x 20'. The workshop room out back is 10' x 12'.
A big part of the space will be mechanical support for my car hobby. I currently have a Jeep and enjoy wrenching and updating it. Until recently, I had an MGA, and will build another sometime in the not so distant future, I hope. In support of this hobby, part of the shop will be metal working. I have some fundamental metal shop tools, and a welder.
I also design and build audio speakers as a hobby. This entails woodworking and electronics. My woodworking station is centered around a radial arm saw, then the rest are primarily hand tools. I do have and use a router table. The woodworking extends out into wood finishing and painting.
The final space is typical home maintenance... garden tools, leaf blower, edger, lawn mower and so on...
Did I mention that we want to park two cars in the garage too? lol...