Should the agenda be its own page or on the invitation?
On the invitation, beside the sign-up. The programme is the reason people commit, so putting it next to the button lets interest turn into a place claimed in the same visit.
How much detail does each session row need?
Enough to answer what, who, and when: a recognisable title, the speaker's name, and a time a distant attendee can place. Beyond that belongs in a description, not the schedule row.
Can I see interest per session, not just a total?
You read the registration list against the programme you published, which shows the shape of who signed up. It is the list itself, not a separate analytics tool.
What if sessions overlap in time?
Show it plainly. List the parallel sessions at the same start time so a person can choose, and keep the sign-up near the list so the choice turns into a claimed place.
Do speakers need to be on the agenda page?
It helps more than almost anything else. A familiar name attached to a session is what makes a reader decide that row is for them and register.