I think generally speaking, youtube videos should be used to inform decisions/general guidance rather than "do X and you'll get Z". Raiden's damage output goes up tremendously with C2-C3. If I wasn't so low on primos and intent on saving for Hu Tao I'd try to get her C3
I have her at C2, no Engulfing Lightning (I'm using Skyward Spine until I can get The Catch), no C6 Sara (mine is C2), no crowned Bennett (mine isn't even on his last ascension yet), however, I did manage to hit 289K on the primo geo vishap boss. I did use Sucrose with 4-piece VV set in my rotation (swirled lightning to reduce the boss resistance to it) and I used Mona rather than Sara.
I'll have to try Mona/Sucrose as I have both.
Fred.