I'm somewhat out of touch with model railways as it's been 10 years since my last attempt at a layout. I intend to use PECO Code 100 as this is easily available and relatively cheap. I've decided to use curved points in the corners of the layout to increase the lengths of the straight sections as much as possible. This layout is intended mostly to display static trains, but with each being on a passing loop so that one train can be freely running around the room.

If my measuring is correct, this should allow for 4 trains of varying length to be displayed, while a 5th is able to run around the track. 2 would need to be no longer than 3' as that's the shortest passing loop section, 1 more could be up to 6', and 2 more could be up to 9' in length, although at this time I have no trains even remotely that long.
The layout will be DC as my stock is all older stuff, and a layout this simple would get minimal benefit from DCC at a considerable cost to upgrade my fleet. The points themselves should be sufficient to switch power between the passing loops, although I've never built a layout with this much track before so I'll see if I need any additional wiring solutions, such as a power bus. I don't know if this would help ensure consistent power all the way around the circuit or if it'd be redundant in this case.
I'm going to post updates once I start building the shelves and laying the track in the next couple of months. I welcome your comments and advice in the meantime!