This is the room where I will be setting up. (just done quickly while at work on lunch)...
This is just generic :
Leaving the door alone (if re-hanging to open outwards is a possibility, a bit more space opens up,) in OO or N the right hand wall looks inviting for a nice straight terminus, essentially on a shelf, at bottom right just clearing door and then not growing so wide as to restrict access.
The squarish section remaining looks inviting again for an around the walls mainline, single or double, probably a little lower than the terminus on the right wall so a storage line or two can be hidden there, underneath.
Just where the room narrows is where the main oval will require a movable bridge, or flap section, or gate section, would be required to give access to the central operating area.
(Unless you are young and flexible and happy to duck. But you will get older.)
Somewhere on the main line there would need to be a means of turning trains round to get them heading back towards the terminus.
A through station with one or more terminal bays, probably.
In N a return loop would be feasible, but would not be easy to do here in 00: just too wide!
In N, as ParkeNd has shown, the idea of a single board without a central operating area is more viable.
And detail and appearance isn't an issue.
With N, a single rectangular board across the room at the drawing's top edge might excellent (with the temptation for a narrow branch line to creep back down that right hand wall, of course, perhaps later on,) A triangular junction as it joined the main line would provide it's own return loop.
Definitely more room for choice with track plans in N, and that opens up more possibility of modelling or taking inspiration from, a real location.
With 00 you will find yourself more designing to get the best from the room, which is a somewhat different challenge.
If you don't need an oval where trains can be left to run... even more possibilities.
Sorry, this is moving away somewhat from the N / 00 question.
(There's a separate section for track planning!)