I got two 4gb sticks https://ca.pcpartpicker.com/product/CrTmP6/a-data-memory-ax3u1600w4g11dd and I want to add some more ram, would a single 8gb stick work and how similar does it need to be settings wise, if you know one that would work please let me know and the xpg 1.0 is discontinued so I cant get that.
All of these people are talking about speed/timing.. Your motherboard will downsync the timing/speed to the slowest module in your build which unless they are widly different, will have very little impact on performance (un-noticeably, especially in games). With that being said, you should at least try to match timing/speed to eliminate any possibilities of errors. So don't just go buy a random stick.
I can pretty much guarantee you (90%) that adding a 1x8GB stick to your existing setup will work (assuming your motherboard supports it). However, you do need to consider that by adding a single stick to a dual channel set up that you will no longer have dual channel capability.. This isn't extremely important in most games (nowadays), but some games and plenty of desktop applications definitely make use of dual channel bandwidth.
Let me know if you have any additional questions.
Anything with the same speed and preferably the exact same CAS timings should work. Can't guarantee it'll work until you try it, all motherboards and RAM are different.
Just get another 2x4gb kit, DDR3 1600MHz with the same CAS timing of 11.
RAM like these will work: https://pcpartpicker.com/products/compare/6jp323,ZPnG3C,tmYXsY,svXfrH/
but if you got a kit that was 1866Mhz, it would simply slow down to 1600Mhz and slow down to those timings.
Sometimes it works sometimes it doesnt you can try. Ive tried 2 times and once it worked other time didnt even though it was the same brand RAM with same timings and speed, a 2x4gb and 1x8gb still didnt work. Better off getting new RAM and selling the old.