Module development and code questions

I'm trying to figure out the best way to store data that will be used for reporting.  The results of some action on the site by a user.  In D7 I just used a custom table and queries, but I'd like to see if there's a better way with D8.  I also want to make sure it integrates well with Views.

I'm trying to build a module that authenticates a user to Drupal based on a HTTP header added by a reverse proxy.

I read that Drupal 8 has a new authentication API, so I initially tried using that. I only half expected it to work, and sure enough, it only half worked: the user was authenticated, but could not submit any forms because (I guess) the CSRF token is linked to a session ID, which they didn't have.

I'm working on trying to allow users to hide their profile from other users or anonymous users. Unfortunately I haven't been able to find any way to do something like this. Would I need to develop my own module to do this? If so, what might I need to have to ensure I can make my module a success? I haven't built a module before, but I'm willing to give it a shot.

Among others, Drush 9.3.0 lists these commands:

Hello everyone,

I have a problem with my ajax submit form