RAM recommendations for new build

[purevw]

I am looking for opinions please.
I am building a new Ryzen unit and am looking for advise on RAM. I run OPENsuse Linux. The motherboard will be an ASUS Crosshair VI Hero.
There is a saying in Linux that free RAM is bad RAM, and most flavors of Linux seem to act on that saying. I currently have 8 cores running at 2.6Ghz on an old Tyan board with 32GB of RAM. After a time, all 32GB are being used, mostly by the disc cache.
Due to limitations in Ryzen, according to AMD, if I fill all 4 slots with dual channel/dual rank modules, I'll be limited to a RAM speed of 1866 (I thought that DDR4 started at 2166?). If I only populate 2 of 4 RAM the slots, many say that 3200 is possible, although AMD says 2667. But in most overclocking videos I have watched, they use only 16GB when overclocking to 3200.
The sole reason for my new build is for video and audio work. I use Handbrake almost exclusively for the video work. I almost never game, other than play with a flight sim. I am looking for faster encoding as well as lowering the power consumption and heat generated. My Tyan has 4 95 watt TDP CPUs and with Ryzen, I can do the same job faster with a single 95 watt TDP CPU.
My question is: Considering Linux very much likes to fill RAM and I'll be using Handbrake for video editing, am I better off with a lower amount of faster RAM or larger/slower modules?

[s55]

It's not going to make significant difference either way. HandBrake typically won't ever use more than 3GB and as little as 200MB for SD content.

As far as not having "free" ram, it doesn't matter as long as it's available for use. The system will free up cached ram for HandBrake so it's a non issue.

[nhyone]

I read a review comparing RAM from DDR4-2133 to DDR4-3200. As usual, memory benchmark shows a significant difference. There is very little difference (<1%) outside of specific uses, such as some games and file compression. The 7z benchmark is 3+% faster. The x264 pass-2 benchmark, which is compute-bound, shows no difference.

More than RAM, the Ryzen 7 1800X has a two "core complex" of 4 cores each (with separate L3 cache). This makes it like a two physical CPU setup. It might be better to encode two videos at once, each using 4 cores, for maximum efficiency. The last thing you want is L3 cache thrashing, which is what will happen when the threads bounce from one core complex to the other.

[purevw]

My primary concern is frame rates. I'll be going from 8 cores at 2.6GHz to 8 (2 thread) cores running at up to 4.0Ghz, which will no doubt help. I wasn't clear on how much RAM could affect performance and what I might expect as far as speed versus size. I may go ahead and max out the RAM (64GB) with 2133 and buy a couple of modules of G.Skill 3200 that they advertize as "Ryzen optimized", just for comparison and benchmarking purposes.
The Ryzen platform is so new that updated BIOS, specifications, and stability optimizations are coming out rapidly. I guess it will be a learning experience.

[Woodstock]

And the extra threads aren't going to help matters, because handbrake pretty much tops out at 8 threads. The main thing is going to be the clock speed increase.

If it were me, I'd build it with 32GB of RAM, not for handbrake's sake, but for anything you might run while handbrake is churning away.