For me,
Margaret and
Marguerite are both sophisticated, distant and aloof.
Margot has a whole different vibe, being friendly and both sweet and tangy. I like this one best, but way way better without the silent T. Some people said "margot" is close to "maggot".
Margo isn't though :)
The only nicknames I really like for them is
Meg. I like Mig too, but that's from a book as a nn for
Margaret and I've never heard it anywhere else so maybe it doesn't count.