High quality battery?

After the 2 generation mark, a lot of the open market batteries start to become compromised due to lower price per unit expectations and consumers being less willing to pay for quality, so corners tend to be cut. Once you get to the point the phone is 3-4+ generations old, the majority of them are garbage. I would keep your expectations realistic based on those numbers since you’re in-between the point where they’re good or garbage. You may not find what you want and may need to settle.

Out of all the batteries, the ones from iFixit are going to be the best quality. If you’re adamant on not wanting to risk getting garbage, stay away from eBay since it’s mostly used as a clearing house for junk batteries. The eBay batteries are fine for an older phone that isn’t worth enough to care but you still want (or need) to get a new one, but on these newer phones you can (and should) do better then eBay. My S6 Edge+ has an eBay battery, but the screen has 2 dead spots in the panel and multiple spider web cracks.