Simple Text email Vs Designer HTML🎨. Which one converts better?

I have read on some marketing websites that simple text emails have a higher personal touch. I have been using simple emails for the last 2-3 months and the results have been good.

However, as a designer, I couldn't resist the urge to beautify the plain-looking simple text emails. So, I designed an email template with an auto layout in Figma and then converted it to HTML using a plugin. I manually polished it by adjusting the CSS a little bit as the plugin's output was not perfect. Finally, I replaced the simple text email with this HTML design. Now, I am testing it.

What are your thoughts on it?
Should I stick with simple text emails or use HTML?