Before and during, on one address
The practical build is one page rather than a stack of them. My Joyfullday's webinar invite gives the programme, the speaker section, the registration with tracked replies, and the private access links the same home, so the shift from persuading to letting people in never changes the URL.
Where a bigger gathering suits it, put the livestream link on the page so remote guests have their own door, and keep the join instructions short enough that nobody needs to ask. A page that works both before and during is a virtual event's only reliable front desk.