Do these have a noise reduction rating?

The product information gives no NRR or SNR figure. Without a published rating you cannot compare them directly with muffs that list one, so treat the protection level as unverified.

No. They are passive muffs with no microphones, amplification or sound compression, so you hear everything muffled rather than boosted.

Can I wear them swimming?

They are over-ear muffs, not earplugs, and nothing states they are waterproof or rated for submersion. For swimming, sealed earplugs are the usual choice.

Are they good for sleeping?

They can block noise, but the cups are bulky and press against a pillow when you lie on your side. Side sleepers often prefer low-profile muffs or foam plugs.

How do they compare with electronic muffs?

Electronic muffs let you hear speech and range commands while cutting loud shots. These are passive, so they are simpler and have nothing to power, but they muffle conversation.