Not exactly sure how Muun wallet works, but iiuc in muun you only have a onchain balance and if you pay a lightning invoice its a swap :? Also Muun has no marketplace for swap providers, so you can only swap with them and have to pay their fee.

In Electrum you can open lightning channels, and as a result you have a separate onchain and lightning balance. And if you want to move sats between lightning and onchain you can either open/close channels or do a swap (with a counterparty you can discover via nostr and choose the cheapest or e.g. most reputable from).