Salmon rods are usually softer tips, the actions are moderate- mod-fast-med fast. This is to protect light lines and running fish. The rated lure weights are lighter and the line rating is lower. ( don’t over think those though, that is only a guideline)
Muskie rods usually have more power because you are using heavier baits and fishing them harder. They are usually Fast action, they have more backbone and are usually higher graphite to give the rod faster deflection. (usually again there are exceptions to all of this).