2133MHz is enought ur laptop dont support 2400MHz. Kingston is reliable brand should be no issue.

Ummm like i mention for value ram u won't need to consider all those voltage due to it comes as the minimum but for gaming yes because u need to OC. For laptop its not recommended too oc unless u want to burn ur table,bed or lap.(im just exegerating) So don't hastle urself thinking to much. Your existing Skhynix RAM is consider good but Kingston is better.
Get the same speed of your existing ram. U can't go wrong.

1. Your laptop max ram config is 2133Mhz DDR4
2. Voltage consideration is required if u have an OC Mobo where its mostly use for desktop computing.
- If u say ur laptop is ASUS with watercooler then i will recommend u to get a higher frequency ram.
- The higher the frequency the expensive its.
- Non gaming series won't benefit much from higher frequency. U end up wasting extra money on non visual experience coz u won't see the different.