What is the Recommended Size for my Banners?

Site URL: https://bluebird-porcupine-yzdg.squarespace.com/desktop

Hello, I would like to know what is the ideal banner size that would look great on my site? I'm using version 7.1.

I believe my current banner designs are around 3840px by 2000px?

But my banners do look pretty big on site. If I reduce the Section Height settings to M or S, I do lose quite a bit of my background image. Please advise.

My site page is here: https://bluebird-porcupine-yzdg.squarespace.com/desktop

Pword = bluebird

Many thanks,

Best,

Faiz