Usually you won't notice any FPS drop, since it's only textures. Well, if your ram is heavly overloaded allready you might exceed the limits and you will lag, but most likely you won't notice the difference. The standar LFS, and fully highres stuff version on my computer only had 4-5FPS difference, and when you having 200+ avarage that is the least problem.
But again, if your computer allready struggelig you might consider it, or just test it out, would probally take some more FPS's then.