I've been to a handful of closing performances & I don't ever remember there being special curtain speeches. (The only time I recall that happening is during Emma Stone's last performance in Cabaret, oddly enough.).
I think the festivities you speak of-- like speeches & production curtain calls-- only happen for really long running shows. Like when they've become institutions.
But yes, as others mentioned, I did find the audience to be a lot more enthusiastic. Almost obnoxiously so.
But I think you'll be fine for Sunday in the Park with George. It's a limited run, for starters. So as soon as the show was announced there was always a "final performance." And I could be wrong, but I don't really think there are any SITPWG groupies out there.