It's mediocre. It's the same platform as this AG-650M that was reviewed.
https://www.jonnyguru.com/blog/2018/07/16/apexgaming-ag-650m-650w-power-supply/
Is it the worst thing ever? Probably not, though they cheaped out on anything wouldn't get them the efficiency badge and it's made by a bargain basement manufacturer (Deer/Solytech). But at least the 80 Plus isn't faked, which is common among the worst of the worst. It might be acceptable on a cheaper PC, but there's zero good reason to pair this with a 2070 Super and a 3900X. I'd absolutely return this.
I don't think I can return it. Its past amazon's return date and I'm broke as hell after the upgrades :/
Should I save up and pick up a new one and use this one for now? Or should I not even risk it until I can get a better one?
Also does anyone know how much power I'd need for a 2070 super and 3900x? I've been told 750 is more than enough but wanted a more specific answer so I know what I should shoot for in the future
It's not in the dumpster-on-fire tier, so it's probably OK to use until you can get something better (and you really should, it's the most important part of a build). I would refrain from doing any playing with overclocking and the like, however. Treat it your PC like a car you're borrowing from a friend, so no road trips across the country at high speeds.