The only time that I upgrade on my end is when the forum software supports it and it's stable enough to go ahead 🙂 doesn't mean it's super fast or anything, feels the same Xd.
Your Cpanel should have the option to change PHP, if not then your host provider doesn't support the new version yet. Before changing and updating you would need to edit other files in your root other wise you upgrade and the site is like, Mehh, not today I won't work.