The spare version usually wins
The instinct is to fill the page, because an empty section feels like an unfinished job. A webinar page is the exception. A guest decides in a few seconds whether an hour of their evening is worth an hour of yours, and that decision is made by four things: what the session is, when it starts, what happens in it, and how they put their name down. Everything else on the page either supports those four or competes with them.
Simple is not thin. Three agenda chapters with durations, a paragraph about the speaker and an honest promise is a serious invitation. What gets cut is decoration, the wall of questions, and the second promise nobody intends to keep.