What is wrong with a single public link?
It carries no names and no limit. Whoever holds it can pass it on, so the host first learns the true headcount as people arrive. A named link keeps the room the size you chose and attaches the guest list to it.
Do private links stop attendees forwarding them?
They cannot police that, and you should not need them to. The link is issued to a name on your list, so the room's guest list is the record. A forwarded link widens nothing structurally, and the reminders still go to registrants you know.
How many reminders are too many?
For most sessions, three: one confirming the place and link right after registration, one the day before, and one shortly before the start. More than that invites people to stop reading, which is precisely the failure reminders exist to prevent.
Can capacity change after registration opens?
Yes, the tiers are yours to adjust while the page stays the same address. If demand surprises you, raise the cap and the list keeps going; if the session is full, the page can say so honestly instead of accepting names you cannot seat.
Is this appropriate for a paid ticket?
No. My Joyfullday does not sell tickets or take payments for events. Registration here means free sign-up with name and email against a seat count; if admission is paid, that arrangement belongs somewhere else.