TLDR: Fixes issues where the nether ores wouldn't appear in modded nether biomes. As a result makes Netherite slightly more common.
Netherite tweaks is intended to fix a certain problem that can appear in heavy modpacks with new nether biomes. It will also fix nether quartz & nether gold ore spawning issues as a side-effect.
This mod can also be used in absence of these biome-related issues to make it appear slightly more often on average.
The best place to find Netherite is still y=16, but it can also spawn between y=8-24