to this part. Seeing that, I don't think juhabach would think differently of the pride of their own people. What good is it if it has gotten them annihilated twice (1000 and 200 years ago)? What good is it if it didn't help them win? Juhabach has so far fought an underhanded war where he has stricken down his enemies dishonorably (which is the way to go in a war BTW). He does not give a crap about pride, his quincy are not about that. His quincy are a bunch of dishonorable murderous thugs that would go to any extreme to defeat the enemy. And that is the way juhabach wants them. They do not have the pride of the quincy.
I thought Yhwach's backstory made it pretty clear. He "fixes" (not really) defective people. All these guys had some major issue before they got a piece of his soul. Which would have only fixed the physical aspect not the mental problems like doubt/lack of self worth etc. And getting fixed might have made things worse for some. Like being desperate to cling onto their new power or becoming power hungry because of it. A guy like Gremmy thought he was unrivalled.
Becoming a Stern Ritter involves carving a letter into their souls. We still don`t know what this actually means but to me this sounds like a very invasive, dangerous procedure that leaves the soul damaged and potentially unstable.
It also connects the soul closer to Bach than other Quincies.
We saw the process through uryu, its nothing like that. He drank his blood from a cup IIRC. You are thinking HP. And the process does the exact same opposite of damaging a soul, there was a chapter dedicated to that. The manga described the process as in mending a soul, as in giving it something it lacked. It does create a stronger link to juhabach and somehow leads quincy to death... I would argue that the implied downsides to the whole thing are mostly because juhabach chooses for them to be that way, he could easily just take a non asshole attitude towards it and actually benefit his brethren and also help himself every bit as much.
Gremmy was probably the strongest sternritter. Not much proof on this because we havent seen Hachwalt yet. But judging from the reactions he got from Hach and the others like Bazz B I think hes definitely up there. Personally I think Gremmy could take on Giselle, Candace, the hungry chick all at once because dam hes Gremmy. Only monsters on a whole other league like Kenpachi, Ichigo, Ywach, or Yamamoto could beat him.
But on topic I think there crazy because of power. "With great power comes great responsibility." Otherwise you go nuts.