All of my rail is code 70, some hand laid and the rest are Shinohara.
I had a large N scale layout which I tore out and moved to HO scale over 30 year ago. One of my gripes about N scale next to the lousy locomotives available in the late 70's was the grossly oversize rail. I guess that's why I went with code 70, because it looks so much better.
I have used a number of different brands of rail joiners. I like the Shinohara because they were a bit smaller than others, but a long time ago when I was out of rail joiners and with no hobby shops at all in my area, I used some Atlas N scale rail joiners and they worked just fine. I had to slightly tighten up the joiners on some ME flex track as the web is a bit thinner, but has no problem at all with the Shinohara track.
Walthers has a transition track the goes from code 70 to code 83. I did use some code 83 track in my hidden staging area and used the conversion track, which is 3 to 4 inches long. I think I still have a couple left that I never used.