Both seem to be good, but if you are a beginner, I guess even for a first run, Scenario 1 might be faster since it employs brewed BIAB style that is close to the song. You can directly rewrite the chord structure to abide to different sheet music and then recording bass lines. This could save you time which you would use inputting each note in the second scenario.

Of course, it depends on how difficult your song is, but if it is simple and fast, then you try to work with the Scenario 1, and change it if necessary

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