Points taken.
For the login question, if you add an email to a member you will then have the ability to invite them to join (both chess nut and your club). A person can belong to multiple clubs (i’m currently a member of 2 in my local area). If you invite someone with person-a@gmail.com and they create an account using that email then they will automatically be connected to your club (so they can see the list of upcoming private tournaments and the names of people in the club). If they sign up with a different email like person-a@hotmail.com then they will still connect to your club as long as they clicked the link in their email (which has a unique token that links to your club). If they don’t do that, it gets a little trickier. You’d have to re-invite them with the email they used. You can delete the existing invitation and send a new one with the address they used to sign up. That unhappy path rarely happens (and it is something that will become more friendly soon)