Build on the template at the size it opens at, and do not scale the artboard. The measurements in it are the ones the plant presses from, so resizing moves the trim, fold and spine away from the machine that cuts them.
CMYK at 300 dpi
Set the document to CMYK and keep every placed image at 300 dpi at final size. Artwork built for screens in RGB will shift color on press, and an image that looks sharp on a phone can land soft at sleeve size.
Keep type out of the no-type areas
The template marks where text cannot go. Anything sitting in the trim, the fold or the spine zone can be cut through, folded across or hidden once the sleeve is assembled, so keep words and logos inside the safe area.
One spec, both factories
US and UK orders press to the same specs, so a template is right for either factory. The two 7 inch label templates are the two label styles rather than two regions, and both are valid.