what is the recommended size for "logo"
Max width property of the logo is 180px, and max height property of the logo is 32px. If your logo dimensions are lower than those, the logo will stay in original resolution. If at least one of your logo dimensions is higher than those, the logo will be resized so that one dimension will be at the max length, and the other will be set to keep the original resolution.
If you want your logo to be as big as possible, build it at 180x32 resolution.