Will this ore still be there after I remove this mod?

Existing ore won't disappear, but ore won't spawn in newly generated chunks.

... I don't really know why you'd want to remove it anyway.

Because every 5 second map generator update is up down when this mod update,is this permanent?

I just finished build base on vulcanite planet,and come back to nauvis

Then this happen

Because every 5 second map generator update is up down when this mod update

I don't understand exactly what you mean by this.

Whenever the game generates chunks (from exploring, pollution spread, using the satellite view, planet scanning, etc), there will be a performance impact from this mod because it has to do everything twice. If you aren't doing anything that generates chunks, there should be no performance impact.