Not much changes in terms of the footprint, except that the minimum radius is smaller so the “blobs” can be smaller. That opens up aisles, allows longer straightaways for yards, etc.
As with a number of other issues, this will depend on the type of railroading you’d like to incorporate, era, locale, etc. As noted earlier, if you can share more about what you’d like to see on the layout, it will help others help you. That piece of the puzzle is still missing.
The ratio of N scale to HO scale is 160 to 87.1 – so N scale is about 55% of HO. A 28" radius curve in HO would be 15 1/4" radius in N and would handle most equipment. Broader curves look better with longer equipment.
Although it requires knowing more about what equipment you plan to run, the Layout Design SIG’s curve radius rule-of-thumb can be handy.
The “G” still works and provides walk-in access. Double-sided backdrops will divide the benchwork into a separate scene on each side. You can go multiple passes through the scene for a longer run, if that’s what you want (or multi-deck, a much bigger undertaking).
With the smaller minimum radius for N scale I’d probably not bother with the donut. But if I did, I’d think about docking the donut to one wall as I posted earlier. But the donut is not walk-in – and really helps most with radii that are broader relative to the roo