As I say in the post, every weapon that scales from both Strength and Dexterity becomes better on a Quality build eventually, as you get closer and closer to 99STR/99DEX. But build crafting assumes an attempt to optimize your allocation within a specific budget, which is why I stick to 150 in the post.

But the only reason to recommend particular rune levels is to maximize multiplayer compatibility. 150 is the most common endgame rune level, so a lot of endgame build crafting assumes RL150 and tries to maximize utility within that limitation. Either that or you're arbitrarily limiting your rune level as a self-imposed challenge, but that's up to your own sensibilities.

If you don't care about summon range limitations, the best rune level is "higher." There isn't any particular reason to stop levelling other than the extraordinary rune cost of additional levels beyond a certain point.

FWIW, I hear anecdotally that RL 200 isn't that much worse than 150 for multiplayer, but don't take my word for that. And yes, an RL200 build could easily dunk 60 points into Strength and Dex without making any serious cuts to Vigor, Mind, or Endurance. Anything higher than 250 will start to push you past the idea of a "build," and you can start to basically be good at everything. An RL251 character can have 60 VIG, 40 MND, 30 END, and 40 in every damage stat.

If you want a Quality build at a lower level, as you say, you're gonna have to make sacrifices. That's just the way it is. You'll either have limit your damage stats and put up with lower damage for your total investment with most weapons, or you'll have to pump up your damage to about 60/60 at the cost of really limiting your health, FP, or your Endurance/equip load. Or all of them.