i think u should do both courses coz for website u have to b professional and also have knowledge of color, expert in using graphic content in websites.
yes adobe photoshop is most graphical software for designing website.
Adobe gives u lots of tools to make graphical look and u can make changes by creating
layers of every single object.
Building a website with good content management system makes it a lot easier to
manage than the traditional way of editing and uploading to make changes to a website.