I personally find the header logo dimension too small to my personal liking.
The maximum dimension permitted is 250px.
I would like to increase the size (while viewing on desktop) without affecting the mobile.
How should I go from here?
Without seeing your website, I can only assume the same as another thread, your image has alot of empty/whitespace.
See my reply here https://community.shopify.com/c/Shopify-Design/How-do-i-make-my-logo-on-my-header-bigger-and-also-ma...
250px is ALOT, so this would be an empty space/white space issue on your logo.