Whichever Endministrator you pick in Arknights: Endfield, they’re the same mysterious amnesiac waking up on Talos-2. If you’re torn between the two forms, don’t sweat it — you can switch later once the story lets you.
How to change your Endministrator’s form in Arknights: Endfield
You’ll need to push a good way through the opening and hit Authority Level (account level) 15 before swapping becomes an option. The game hard-gates progress there; once you reach 15, the next main story segment unlocks and takes you to the OMV Dijiang ship.
Onboard, you’ll be shown the Stasis Core. That’s the device that lets you switch which Endministrator you’re playing as. There’s a cooldown, though — you can only do this once every 24 hours.
That’s really all there is. Your pick doesn’t affect the story, so you won’t miss anything by sticking with one — and you can always swap later if you feel like a change.