I use muun to aggregate (incoming only) onchain and lightning sats. Once I have a large enough number of sats, I send it onchain to my cold storage or mixer in one transaction to consolidate my utxos. I try not to send lightning payments out using muun because their implementation of submarine swaps can cause high fees even when using lightning. Each transaction OUT requires both a lightning and onchain transaction. Lightning transactions in are fine because the sender pays the normal lightning fees. Muun is great for aggregating all those little zaps into one big(ger) onchain utxo.