I don't have the switch version, so I can't give a direct answer, but I can tell you how to test the submit scores question.

The way we disable score submission on PC is by putting steam in offline mode, so that it can't connect to the internet. So on switch, I would try to disconnect the switch from the internet, and then try playing an individual level. If the score submission text doesn't come up, then you're good to do runs.

And if you have any other questions, I would recommend going over to the community discord. It's pretty active (depending on the time of day) and questions usually get answered pretty quickly.

this is the permanent invite link to the discord: http://discord.gg/nplusplus