First of all, major brands are all ok with lifetime warranty.
But to correct some misconceptions.
a) ryzen is dual channel, there is no value with a 4 x 4 kit. Plus, a 4 x 4 kit will cost more than a 2 x 8gb kit
b) Ram must be matched.
Ram is sold in kits for a reason.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
The internal workings are designed for the capacity of the kit.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards, can be very sensitive to this.
c) do not buy a single stick. performance is better with dual channel.
d) Not all ram works with ryzen. Take the time to look at your motherboard ram QVL list and buy a kit that is known to be supported.
Or, go to the kingston/patriot... web site and see what ram kits are supported on your motherboard.