UFA's. I heard statistically 6-7th round picks have extremely low odds of making a team. Mainly because the difference in ability between 6/7th round draftees and UFA's a team signs is small. But the $ owed if the make the roster isn't.
Plus as a UFA u get to chose between a few offers when draftees can't. Chiefs is a great spot for Mitch. They're desperate for receivers and might be one of about 5 total teams where the WR spots are wide open. Plus forced to be a running team with a QB with a terrible YPA, TD totals; the Chiefs could use more redzone help so their TE isn't triple teamed. Might work out well for MM