I think of it as a traditionally male name, but all the Devins I know are girls and they spell it [name_u]Devin[/name_u] or [name_u]Devon[/name_u]. I like the [name_u]Devin[/name_u] spelling myself.
From your list of middles, I like [name_u]Devin[/name_u] [name_f]Rose[/name_f] the best. I think I like that it makes the unisex first name more feminine, but it’s not long or frilly enough to be a total mismatch from the unisex first name. [name_u]Devin[/name_u] [name_f]Serena[/name_f] is also nice. You might like:
[name_u]Devin[/name_u] [name_f]Adele[/name_f], [name_u]Devin[/name_u] [name_u]Aubrey[/name_u], [name_u]Devin[/name_u] [name_f]Brielle[/name_f], [name_u]Devin[/name_u] [name_f]Charlotte[/name_f], [name_u]Devin[/name_u] [name_f]Elyse[/name_f], [name_u]Devin[/name_u] [name_f]Estelle[/name_f], [name_u]Devin[/name_u] [name_f]Felicity[/name_f], [name_u]Devin[/name_u] [name_f]Georgina[/name_f], [name_u]Devin[/name_u] [name_f]Grace[/name_f], [name_u]Devin[/name_u] [name_f]Hannah[/name_f], [name_u]Devin[/name_u] [name_f]Hope[/name_f], [name_u]Devin[/name_u] [name_f]Laurel[/name_f], [name_u]Devin[/name_u] [name_f]Leona[/name_f], [name_u]Devin[/name_u] [name_f]Louise[/name_f], [name_u]Devin[/name_u] [name_f]Lucy[/name_f], [name_u]Devin[/name_u] [name_f]Mallory[/name_f], [name_u]Devin[/name_u] [name_f]Margot[/name_f], [name_u]Devin[/name_u] [name_f]Matilda[/name_f], [name_u]Devin[/name_u] [name_f]Miranda[/name_f], [name_u]Devin[/name_u] [name_f]Nicole[/name_f], [name_u]Devin[/name_u] [name_f]Noelle[/name_f], [name_u]Devin[/name_u] [name_f]Olivia[/name_f], [name_u]Devin[/name_u] [name_f]Paige[/name_f], [name_u]Devin[/name_u] [name_f]Pearl[/name_f], [name_u]Devin[/name_u] [name_f]Rachel[/name_f], [name_u]Devin[/name_u] [name_f]Regina[/name_f], [name_u]Devin[/name_u] [name_u]Ruby[/name_u], [name_u]Devin[/name_u] [name_f]Sabrina[/name_f], [name_u]Devin[/name_u] [name_f]Sophia[/name_f], [name_u]Devin[/name_u] [name_f]Violet[/name_f], [name_u]Devin[/name_u] [name_f]Willow[/name_f]
I think it works as an honor name for [name_m]Dave[/name_m].