DL&W Pete, welcome to S scale! That question you just posed is one we would all like to have answered. What will happen to the Showcase Line? MTH purchased the Showcase line from SHS and except for the packaging all the track products are identical. So when searching for track search as SHS/MTH. MTH makes 19", 24" and 29" radius curves, uncouplers, bumpers, action tracks and 19"radius turnouts. They make 5", 10" and 15" straight sections. They also of course make flex track.
My layout is built with all MTH flex track. The layout is basically scale except for the .138 rail rather than code 83. I did that so I could run Lionel American Flyer engines. All the Legacy engines beginning with the Y-3 and newer will run on DCC. If you cannot find MTH flex just buy the Fox Valley flex, it has the same .138 rail height. Fox Valley also makes excellent #5 turnouts.
Since I needed a lot of #6 and #8 turnouts, I paid to have them custom made for my layout using the MTH rail we stripped from their flex track.
There are several very experienced S scalers here, some of whom have already provided information. Technically I am a High Rail operator since I have .138" rail on my layout. However I can run all but the longest wheelbase scale equipment on my layout.
Thank you @AmFlyer,
I have had these AM E8's for two years now, still have not been on a track or seen power yet. I love the size of these engines when you put them next to HO and see the difference with O. The size looks "just right", I am going to enjoy this new journey into S scale.