Which one is better designed for youtube thumbnail

Change the text colour as well. It merges with the yellow colour. Use some bright colours for text

2nd one because the first one looks like the image is elongated. My opinion is you can change the arrow or remove it because it is off from the image

Add CTA in second one too. And make "srishti ka rahsya" as the main header. It's a good way to catch attention. I missed it in first glance.