Is it still legal is I play it on my xbox, but I stream my xbox to my computer using console compainion?

I believe so.
When you submit the run just make sure to pick the XBox option that's right for you.

Playing on xbox is fine and so is using the console companion app. That how i stream if i need to use livesplit. Also like Arlan Kels said make sure to select xbox as your platform

Might I ask how you record ur Xbox and live split at the same time do you use game bar to record one and then use another thing to record the other? Or do u some how record both with game bar or do u not use game bar at all?