Hardware recommendations for running VB

[Shmu26]

I am building a system on which I intend to run a linux host and a windows 10 guest.
I do not make heavy use of processor-intensive applications.
What are hardware recommendations -- anything in particular that doesn't play well with VB, and does some particular hardware enhance performance?
Should I get two SSDs, one for the host and one for the guest, or one big one?
I am thinking about i7, ninth gen. I have no special need for a GPU. Does VM run better with discrete graphics? Will seamless mode work better with discrete graphics?
I am thinking of 16 GB RAM.

[scottgus1]

I have an Intel I5-750 from 2009, runs guests just fine. A more recent CPU should be excellent.

Hyperthreads do not help when running Virtualbox guests. So the non-hyperthreaded core count is the "core count" you should use when deciding how many guests you can run. A four core hyperthreaded I7 shows as 8 cores in Task Manager but only has 4 cores for Virtualbox purposes.

Guests tend to run best in the minimum number of CPU cores that they can process their data with. More cores slows down a guest, due to extra scheduling oversight on the host. If you put data that can fill up two cores on a four core guest, the data will process slower than it would on a two core guest.

Optimum guest core provisioning is: all guest cores + 1 for the host <= total non-hyperthreaded core count. The guests do not actually "take" the cores from the host, but they can fill up the cores. If the host doesn't have a free core that no guest running at 100% can access, then the host can get unstable. (This is a little flexible: I have run 2 two-core guests and a 1-core guest, total 5 cores for guests, on a four-core host and had no trouble. The reason for no trouble was because the guests weren't all 100% at the same time. If they did, the host would go south. It's a risk assessment.)

The more memory the better, it's simple addition: whatever each guest is set for + what the host needs to operate nicely <= amount of host memory in the RAM sticks.

If the host disk is an SSD, go ahead and pile the guests on. You should not need to have a separate SSD for the guest OS, unless space is needed. If it's a platter drive, my experience is that two modern OS's booting on one platter drive will be the limit. Add a third and disk timeout errors and/or OS hangs & BSODs will happen.

[Pernat1y]

Disk performance is really crucial, so get good SSD.
Then RAM size. 16 GB is fine if you are not planning on running many apps or some soft of java-based servers
Then CPU. Intel i5/i7 will be enough (or AMD Ryzen 3/5/7).
Discrete GPU is not required, but make sure that there are drivers for your Linux distro. Should not be the problem, but just to make sure.