[name_m]Calvin[/name_m] - Agree with you on sounding like Vivi@n. Also too many letters shared with Vivi@n.
[name_u]Davis[/name_u] - [name_u]Will[/name_u] almost always be mistaken for Dav!d (USA). Wouldn’t cross my mind to nn it.
[name_u]Griffin[/name_u] - Definitely heavy on the masc. Would honestly have a hard time remembering nn’s.
[name_m]Hugo[/name_m] - Vivi@n’s also french (or at least the ‘fancier’ spelling is). Very good name.
TL;DR: [name_f]My[/name_f] vote’s [name_m]Hugo[/name_m]