About the scrunchable scarf

Thanks to finding this forum, I have been introduced to the scrunchable scarf! I am very interested in making one of these.

I am a beginner knitter, I have made two scarves, with garter stitch only. I am learning to perl and feel I am ready to take on a little bit more difficult scarf!

What I understand about the scrunchable scarf is that it is K2 P1 and it the number of stitches has to be a multiple of 3.
I was thinking about doing 21 stitches because the last scarf I made with the same yarn, I made 26 stitches across and it was just a little two wide, but that was just garter stitch - don’t know if that makes a difference.

Anyways, what I am wondering is, do I ALWAYS start with knit stitch on each row?
So basically would my scarf look like this if I did 21 stitches?:
… and so on?

I just want to make sure I am doing this right before I start, ya know?
Before i read anything about this scrunchable scarf I was going to do a ribbed scarf by doing K2P2… could I do that anyway I wanted like K3P3… etc…?
Thanks so so much
I am really excited to get started!