One evening is genuinely enough
With the date and venue settled, an invitation is an evening's work. Design, wording, reply settings โ an hour of decisions, then send. The build balloons only when the page and the RSVP are treated as two separate projects; together they are one pass, because you write the invitation knowing exactly what guests will answer on it. While you are in there, decide what the reply should ask for: anything you do not genuinely use, leave out โ guests answer short forms gladly and avoid long ones.
And replies on the same page mean nothing to reconcile. A confirmation is a tick against a name, a plus-one arrives inside your limit, and the food notes sit where the heads they belong to sit.