What part should I upgrade?

[MiRai]

If your Mboard has 4 DIMM slots just get 16gb RAM and upgrade later if needed.

Recently, there has been no shortage of people coming into the ISBoxer Discord with performance issues, only to realize that 16GB of RAM is not enough for their setup. We saw this becoming an issue in Legion, and since then I've always recommended 32GB for 5-boxing, because if you want to turn up settings, use a bunch of add-ons, and/or keep a bunch of browser tabs open in the background, then you're going to need more than 16GB of RAM.

Also, I would also not recommend mixing and matching sets of RAM since it can lead to issues, especially when it comes to using XMP.

[Kayley]

Recently, there has been no shortage of people coming into the ISBoxer Discord with performance issues, only to realize that 16GB of RAM is not enough for their setup. We saw this becoming an issue in Legion, and since then I've always recommended 32GB for 5-boxing, because if you want to turn up settings, use a bunch of add-ons, and/or keep a bunch of browser tabs open in the background, then you're going to need more than 16GB of RAM.

Also, I would also not recommend mixing and matching sets of RAM since it can lead to issues, especially when it comes to using XMP.

I would never suggest mixing RAM, I just meant buying more of the same at a later date.
Just figured 2GB of RAM per client, 4GB for a bloated windows install and we're good. However, I won't make the same mistake and disagree with you like last time haha; you've done the homework. 32GB is it

[MiRai]

I would never suggest mixing RAM, I just meant buying more of the same at a later date.

I'm not trying to jump on you about this, but that's still mixing RAM.

For a long time, I was under the impression that RAM "kits" were nothing more than just RAM sold together for the sake of marketing so that they could charge more money, and maybe it is when it comes to certain low-end manufacturers. However, Asus has a sticky post on their X99 forum talking about why mixing any RAM sets is bad—regardless of manufacturer/speed/timings/etc—and it's because the RAM kits are specifically binned and tested together to guarantee compatibility at the speed, timings, and density at which they're sold.

An additional side note with "buying more at a later date," is that there's no guarantee that you'll be able to find that particular set of RAM at a later point in time. You may be purchasing 14-14-14-32 3000MHz RAM, in white, but later when you want to buy the same white colored kit, it may be EOL and have been replaced with another kit with a slightly different set of timings, and therefore now you're SOL.

To be fair, this is really only an issue when people want to overclock their RAM (i.e. use XMP), because all RAM should just work together when at the bone-stock speed, but after what Asus posted a few years ago, I will always recommend that people buy the amount of RAM, in one kit, at the time of purchase.