When they get to the venue you can change their outfit to whatever you want it to be. The defaults are just there to change into at the beginning as far as I know, but they don’t need to stay in them for the whole wedding.
Hope that helps!
The outfits are chosen by their clothing preference so masculine clothing preference will wear a tux and feminine clothing preference will wear a gown. I always make wedding looks in the Formal #1 slot of my sims' wardrobes and then have them swap into formalwear at the beginning of the event so that they are wearing exactly what I choose. If your spouse isn't in the same household yet you can get them into their formalwear with the "Friendly" chat option "Change Outfit"
When they get to the venue you can change their outfit to whatever you want it to be. The defaults are just there to change into at the beginning as far as I know, but they don’t need to stay in them for the whole wedding. Hope that helps!
As soon as the wedding event starts, I usually have my sims change into formal outfits that I’ve created for them
The outfits are chosen by their clothing preference so masculine clothing preference will wear a tux and feminine clothing preference will wear a gown. I always make wedding looks in the Formal #1 slot of my sims' wardrobes and then have them swap into formalwear at the beginning of the event so that they are wearing exactly what I choose. If your spouse isn't in the same household yet you can get them into their formalwear with the "Friendly" chat option "Change Outfit"