1. Your thoughts on the name?
It depends
2. Which gender is it best suited for?
I usually think of it as female but it's very unisex
3. Which spelling?
Regan if you like
King Lear and want to pronounce it "REE-gan" or "REH-gan",
Reagan if you want to pronounce it "RAY-gan" and you don't mind if your baby grows up to ruin the economy and sabotage public health
4. What combos can you think of in either gender?
Normally I'd aim for boyish names for something like this, but the
King Lear association seems to allow more leeway for Regan-on-a-girl:
Regan Talitha Regan AlastrionaRegan CordeliaRegan GabrielaRegan WilhelminaRegan Cecily Regan Colleen Regan MirandaRegan MagdalenaRegan Zinnia
Regan Marko Regan AlexanderRegan Silvanus Regan Cassander Regan Malik Regan MalachiRegan Samwell
Regan BasharRegan EverettRegan Matthias Regan Tam