Custom textures with 512 resolution

I've imported a custom texture 512x512 with normal map, and noticed that it looks really bad on "Low" texture settings. It's probably because engine uses mipmap which is 128x128.
I noticed the official textures are 2048x2048. And on "Low" they are displayed as 512x512.

So what's the correct way for me to import these textures? Should I upscale it to 2048x2048. Or is there some other way?

I've tried to disable mipmaps for this texture but it looks bad at far distances.

Custom textures with 512 resolution