If you use open grid or L-girder benchwork, superelevation is easy to add, including the vertical easements into and out of the curve.
I use 3/4" plywood as a sub-roadbed, but any similar-type material, or even spline roadbed should also work. Install the straight roadbed on either side of the curve by fastening the risers to the joists - leave the last riser beyond both ends of the curve unfastened. Install risers to the underside of the curved roadbed, but don't fasten them to the benchwork just yet. If your curve is on a grade, as most of mine are, raise the roadbed through the curve to the proper height, then mark a pencil line on each riser which corresponds to the top of the benchwork to which it will eventually be fastened. If the track through the curve is to be level, adjust the risers accordingly, then make the lines. Next, choose the riser closest to the mid-point of the curve, raise it to the proper height, then push the bottom end of the riser towards the outside of the curve. Re-align the height line on the riser so that its inner end corresponds to the top of its benchwork member (the height line will be tilted, with the end on the outside of the curve somewhat above the benchwork). I've found that the best way to establish the amount of superelevation is by placing a train on the curve, then adjusting the off-set of the bottom of the riser until it "looks right". I use a C-clamp while I'm making the visual adjustments, then, when I'm satisfied with the appearance, that mid-point riser is screwed to the benchwork. Because the roadbed is torsionally flexible, each riser on either side of the mid-point will now be off-set from the vertical, to diminishing degrees, as the distance from the mid-point increases. Working from the mid-point of the curve, carefully raise each riser so that the inside end of the height mark aligns with the top of the benchwork to which it will be fastened, making sure to not change the angle of off-set, then screw the risers to the benchwork. I did all of mine with the trackwork in place.
Here's a sketch of the layout room:
As you can see, lots of need for curves. The low level trackage at Dunnville and the low speed curve between Lowbanks and Port Maitland aren't superelevated, but all other curves are. Maximum track speed on the layout is 45 mph, but the limit is 30 mph or less in most areas.
Here's a train approaching South Cayuga from Dunnville. While it's not overly apparent in photos, the slight superelevation is definitely noticeable during operations:
A westbound crossing Chippawa Creek, heading for Lowbanks:
Looking south at Dunnville, all of the upper level tracks, including the approach to the coal dealer's siding, have superelevated curves. However, I goofed and used a single wide subroadbed for the two main lines: to be more prototypical, each track should be on its own subroadbed, and superelevated individually.
Here is a couple of views of the roadbed-on-riser method of construct:
And a short on-board video of a train on the curves shown above:
Wayne