Just got a free used W10 box, my first one. Deleting all the crap on it, about to connect internet and update 8 months worth. Ugh.
Created an offline admin account, deleted the other accounts. Do I have to create an online profile with MS? Will they nag me forever or lock out features if I don’t?
Install a business (not home) version of Windows 10 and you should be able to turn off most of it.
During Windows 10 setup, you will be asked a lot of questions. The one word to remember is "no."
Last I checked, setting up a Microsoft account was not absolutely required, though Microsoft certainly tries to convince you to set one up.
I think it ends up being more convenient to just set up the damn account. If necessary you can create a new email account at Microsoft's Outlook.com
All the Features That Require a Microsoft Account in Windows 10:
https://www.howtogeek.com/121975/htg-explains-microsoft-accounts-vs.-local-accounts-in-windows-8/