Sims will slow dance longer. Moreover, failure outcomes (kiss, drop) will no longer occur completely random so they do make more sense.

Batch Parties will not end automatically befor 24 hours and can be held at more venues.

Sims can get married at more venues again.

Tweaks the new social interactions:
weddingpartythrowout - moved to mean socials
congratulate - Sims will no longer congratulate their partner to their own wedding/engagement
askforweddingroles - moved the aks to become officiant/flower pal/… interactions to friedly and added a distinctive thumbnail.
expressdoubts - added more negative outcomes
misc - Various other new interactions will no longer clog the pie menu, some got new thumbnails, interactions will no longer be available on Sims you don't have met.

The walk aisle goal will no also complete if your Sim walks the aisle togehter with another Sim.

Sims will react less bored to weddings.

Your Sims will automatically wear formal wear at wedding and pre wedding partys. For family gathering, there's also an alternate version available where they'll choose party wear. Bach parties remain untouched as they are already set to the appropriate party wear.

Sims will be able to call off weddings until the wedding kiss. Just click on the partner of your Sim during the get married interaction.

The spousal kiss interaction will fail less and if so then due to appropriate moods/traits.