Gateron CJ Light Blue and Gateron Oil King are linear switches that actuate smoothly through the entire keystroke. The CJ Light Blue switches have a slightly higher-pitched sound, but they're less smooth-feeling from the factory without lubing. On the other hand, the Oil Kings are deeper sounding and smoother out of the box. However, they have an opaque black upper housing that will dampen RGB lighting somewhat.
Gateron Ink Black V2 and Gateron Oil King switches are both linear switches. Both switches come pre-lubed from the factory and are well-known for their smoothness and low-pitched sound profiles out of the box. The Ink Black V2 switches have a slightly rounder, more resonant sound. The Oil Kings have a sharper sound and a marginally more lightweight actuation, but the difference is too small to be very noticeable. Note that both switches have dark housings, which significantly limits the brightness of any RGB lighting. However, the Ink Black V2 housings have a smokey finish, making them a bit better for letting out light than the Oil Kings, which are opaque.