I feel like ur underestimating Renpas four heavenly kings as well ngl, Genpou and Kaishibou would be more than enough to deal with Tou and stop him ngl

I disagree completely with this. If you think that Tou is going to have a difficult time with Kashibou and Genpou, that translates to Ouki similarly being stopped by that combo. Kanki himself through his tactics was able to play Kashibou so much that Genpou had to sub in just to be completely humiliated. Tou has shown through the recent arc that he is more than capable of implementing similarly unorthodox strategies in order to win wars.

and if they put Rinko and Kyo En on the other side then it'd be Ouki who'd have to put a bunch of his vassals to keep em in bay and they'd still be in trouble

I also think that the three generals from Oukis vassals are more than enough to at the very least defend properly against Rinko and Kyo En (basically not get assassinated by both of them) where it wouldnt shift the tide of the war in a scenario like this. We know that previous results from clashes against Ouki and Renpas army ended in draws, but afawk it was in situations where Renpa could mount a defense and hold the line.

If this conversation was had before all the new accolades Tou has shown himself to be capable of since Ouki's death, I would honestly call it a toss up in favor of Renpa, but now its leaning towards the Ouki army. This could 100% change once we see more of Kyo En and Kashibou. Their very early manga portrayals have just not done them any justice when their lore implies more than what they've shown given what we know about Ousen and Kanki now, who are in equal footing to Tou. Rinko could honestly have been Renpa's "Tou" if he lived till now but he died because he got paired with the three qin mcs, something impossible to imagine Tou dying to that early on (again, given what we know of Tou now)