Summoning weapons is okay if they're magically/spiritually bound to him, but hammerspace is a no-go. Summoning monsters is a little more tricky-- they can appear here briefly, do their attack, and leave, but they don't have the power to destroy whole cities. So: short animation, not long animation. :)

Warp striking and magic should be just fine. The energy to work magic is coming from somewhere, even if characters might not have access to it, and might not even be sure what it is. I'm not sure if that applies to Noct's ring magic so I'll let you decide.