Hi,
you do not write which exact dual Xeon are you running, imho that settles whether this is still good workstation, viable rendering node, or none.
I will write from experience of running 3 rendering nodes on Z10PE D16 WS, all 2x2698v4.
When I bought them in 2016 (time flies...) 64G(4x16) DDR4 ECC 2133 costed little over 300 Euros, but I was cheap and only bought that much for each node :- ). Then during the past two years, prices of memory ballooned to 700 for same amount, ECC or non-ECC.
In past two months, memory hit their rock-bottom once again and will fall further 15perc. potentially due to Huawei ban.
That means 128GB (8x16GB) are going for 700 Euros right now on eBay, which is fantastic price to be honest.
Now to the compatibility, I don't know if it's the cursed Asus board, but Z10PE generation simply isn't as good as the previous was and when I built the nodes, I went through 3 packages of memory before everything was running smoothly.
Running identical kits but not from single run (i.e two sets) should pose no issue in 99perc. of time, but for Z10PE, that 1perc. happened 3 times in row for me. So I understand the stress...
But to better describe the issue, it will not make your PC less stable and cause occasional issues. It will either boot, or it will not boot. It is that simple. There will be no issues waiting hidden if it boots successfully unless the memory has faulty blocks (you can always run 24hour memtest after installation for peace of mind).
I would still try it. Buy the memory from e-shop so that you can harmlessly return it within 30 days if it won't work.
But first make sure you have the absolute latest bios, microcode updates improve memory compatibility over the time.
Also, you have been running only 4 sticks which for dual-socket platform means you were only running dual-channel. Now the difference between single/dual/quad/etc.. is almost none for majority of applications, but Corona tends to be example where this doesn't apply, it has big demand from memory performance.
5) You Windows is already paging to your SSD, and no kind of SSD will make this even remotely faster. It will always be 100 times slower, with one exception being Optane drive, which will make it only 50 times slower ;- ). PCI-e drives for most part only improve sequential speeds for larger files, they don't improve performance, of anything almost.
With that said, you can buy SSDs so cheaply these days there is no reason not to run 1TB as main-drive. But it will not help you with your memory problem.
Also word of warning, D16 m.2 slot is only PCI-e v2 x2. No reason the place SSDs with high sequential speeds anyway.
One more thing about Windows 7/10, they do like to have paging file space equal to amount of ram and it isn't good idea to shrink it, even with good amount of memory. Windows is very smart about memory allocations nowadays.