Yes there is a panel line that runs down the top and bottom of the fuselage. I find the easiest way to get this is to take a few swipes with your knife along the outer edges of each half before gluing them together, creating a slight V. Easily cleaned up with a scriber if needed.
The machine guns were offset on all models that used the MG 17, which would be up through the G-4, with only the left side protruding. From the G-5 they went to the MG131 and these were even and protruded somewhat.
Jay