Chelsea lack of high quality wingers, Madueke left to Arsenal, Sancho isn't enough to reach the standard.
So, Simons won't be a rival to Palmer in order to play, both of them will play if they have a good quality.
Yes, you're right. There are indeed several wingers, but high-quality and talented potential wingers are very limited. Fortunately, Chelsea just signed Jamie Gittens from Dortmund for a market value of €50 million. He's available as either a left or right winger. That's great news. But the others? Those are all mediocre wingers.