No one would bat an eyelid if you wore any of these to a wedding op (I wouldn’t wear the lilac/grey one though as it’s a bit bridesmaidy)- dressed up with a shrug, heels and clutch they’d be perfectly acceptable.
The comments regarding dresses from H&M not being suitable are just nasty and tone deaf. My wedding was quite a formal affair on a boiling hot day - most of the women wore dresses not dissimilar to what you’ve posted - many wore fascinators or nice headbands. I wouldn’t have given a crap which shop their dresses came from or how much they cost - I was just thrilled everyone came.
Wear whichever one makes you feel good.