Do I need an enclosed emitter pistol optic?

It depends on the role. Open emitter dots like the 507C are excellent for range guns and most carry, and they are cheaper and slightly slimmer. The case for enclosed (509T, EPS Carry, Romeo-X Pro) is reliability in deep concealment and bad weather: a sealed emitter cannot get blocked by lint, sweat, or rain. For a dedicated carry/duty gun, enclosed is the safer choice; for a range or lighter-use pistol, an open 507C is perfectly fine. Either way, run backup iron sights.