Yeah there you go. A 6700k and a 7970 is WAY too much for that PSU. You're lucky it hasn't blown up. Inconsistency in power delivery or insufficent power available will cause crashes in a variety of ways. IDK if you have any issues with windows, that's always the go to on early diagnosis, but you NEED a new PSU.
The 7970 is also pretty older so newer rendering techniques may suffer greatly on it. If you got a new PSU to go with your 3070 that you bough. 99.999% chance you will have a perfectly smooth gaming experience at any settings. Do that before you buy any of this other stuff.
And reinstall windows when you put the new GPU in. DDU is a meme in my opinion, there's always a good chance you're gonna run into issues anyway.
But yeah, in summation, there is no point in buying any of that other stuff. A properly tuned 6700k is still more than enough for any of the games you mentioned, as well as 95% of the games on the market.