I've had good results with long interlocking cleat systems like Hangman. I doubt magnets would hold the weight of my framed work. Mounting board is another topic and contingent on what kind of prints you intend to mount. Gatorboard needs to be sanded in order to accept acrylic adhesive foils; and then you need a high-pressure roller device for the mounting process itself, an expensive item requiring a learning curve. You don't want to use Gator for drymounting with a heat press. You can use it as a stiff backing board behind something already mounted, but there are less expensive alternatives. It's hard to give you an answer without more specifics. Entire handbooks and many tech sheets have been published on mounting board options and how to use them.