Pick one feeling, not a genre
“Rainy afternoon” is a vibe. “Lofi” is not. Write the moment in a few words first, then only add songs that belong in it.
Keep the energy close
The fastest way to break a mood is a song that is suddenly much louder or busier. Keep songs within a narrow range of energy. The vibes here use a measure of loudness and busyness to keep things close.
Shape the order
Start soft, lift a little in the middle and come down at the end. For a sleep playlist, just come down. For a sad day, start low and finish on something lighter.
Mix records, not just songs
Two songs in a row from the same record can sound like an album, not a playlist. Alternate where you can.
Stop at about an hour
Most moods last about that long. An hour also loops well: when it comes back round, you will not mind.
Quick answers
Should a vibe playlist have lyrics?
For background use, instrumentals are easier because they do not compete with talking or reading. All the songs here are instrumental.
How many songs is enough?
Fifteen to twenty-five songs is about an hour of lofi. That is the sweet spot.