5 or 6. Easy
Yeah. 5 is good cause you'll get part of Adele's visibility, and full artistic license/ownership. Write her a song and/or make her a beat and you could parlay that buzz. And if you got a hook it's over

6 is less ownership but you're on a label that will force you in the door if they believe in you so it may work out in the long run. Nothing else is worthwhile
I'd go with 5 cause I wouldn't wanna be mainstream anyway. I'd wanna have a big time single that I could eat off while I did what I wanted musically