I dislike both names strongly. Neither are pleasant namesakes, and the REEEEEE- sounds in the former is nauseating.
Regan is firmly feminine,
Reagan is GN, but I slightly prefer it as a masculine name.
Regan for REE-gan,
Reagan for RAY-gan.
Regan Titania,
Regan Estrella,
Regan Arianna,
Regan AngeliaReagan Fred,
Reagan Fiorenzo,
Reagan Boreas,
Reagan Antonius
masculine list:
https://www.behindthename.com/pnl/191050/124079feminine list:
https://www.behindthename.com/pnl/191050/124080