Hello. Does anybody know the recommended min / max height and width dimensions for the logo?
It depends which of the two variants of the theme you are using. If you are using the second variant ("normal header"), the one shown on the second demo, we recommend to follow similar dimensions to the demo logo, approx. 160px width, and 35-40px height.
If you are using the first variant of the theme ("mobile header"), as shown on the first demo, you can experiment a bit more with the dimensions. width can be between 150 and 250px, height can be bigger too, although we recommend to not exceed 40px for best results.
The idea is that the theme works best with a low profile landscape logo. If your logo is a square, or portrait, you have to make some tests on your own and see what works best to you. The container limits the size of the logo image - if the image is too big, it will be scaled down to fit the container. We recommend to use actual size image and avoid scaling, sometimes scaling introduces bluriness.