Well, there are some aspects you have to consider.
First of the Games:
Overwatch and Fortnite are not too heavy games and will run pretty smoothe on the R5 1500x and 1600. But PUBG.. nah..
Even after the 1.0 PATCH, the game is still not the best game for performance. If you like pubg much, go for an 1600.
Now the critic thing.. streaming
Streaming on the 1500x may cost you the most of its power (depends on which resolution etc. you are streaming).
For streaming/recording I would more likely take the 1600 rather the 1500x.
Third thing: Overclocking
Of course you can get much power out of the 1500x by overclocking too, but good AIR coolers that are good for OC are expensive.
Because they are expensive, you can think two ways:
1. I buy the 1500x and have some money left for OC
2. I buy the 1600 and get stock better performance but may can't OC (You can still buy a cooler thats cheaper but can OC at least a bit)
Fourth thing
Your overall hardware
The 1050ti is a good budget card (but I prefer the 1060, but yeah, you have only 700$ so, okey)
Your PSU AND Motherboard have to be good if you wanna OC.
So if I would consider the things you wanna do with the PC, I would say take the 1600 and at least try to OC it.