Start with how you will carry it
Olight splits neatly by carry style. Pick the body first, then the output.
Flat pocket carry - Arkfeld / ArkPro
The Arkfeld and ArkPro are flat instead of round, so they sit flush in a pocket like a phone. Many add a green laser and UV. This is the modern EDC pick if you want light plus a pointer in one flat body.
Classic round EDC - Baton
The Baton series is the traditional tube light, small enough for a pocket, with a magnetic tail that sticks to metal for hands-free work. A great all-rounder.
Clip-on and hands-free - Oclip and Perun
The Oclip clips to a cap or collar for hands-free light in a tiny package. For real hands-free work and the outdoors, the Perun headlamps give a right-angle body that also works handheld.
Always-on-you - keychain
The i-series keychain lights are the backup you never leave home without - tiny, light, always there.
Then pick the output
More lumens is not always better - see lumens explained. For EDC, a few hundred to ~1,500 lumens covers almost everything, with longer runtime at lower settings.