Not sure how much it applies here, but my 3DS has been using CFW since Fall 2016 with reckless abandon online. I did turn off spotpass and the ability for friends to see what I'm playing, but my activity logs are dirty AF, I use FBI and used to use freeshop quite normally, and all as CIAs. No "stealth mode". Still not banned.
I'm not saying I did anything to prevent it, I'm not saying I'm safe, and again it may not apply to Switch. The real moral of the story is to just accept that a ban may or may not be coming, Nintendo is inconsistent. By hacking at all, you've risked it. But you can't change the past. Just try not to do the insta-ban things like CDNs and Cheating, and enjoy your CFW.
That said, I will wait until we know more about their methods because I want to Smash online.