Swap memory: SSD or HDD?

Hello Comrades,

Thanks for all your advice about setting up Linux. It was a success. The problem is that I'm now I'm intrigued and I'd like to play around a bit more.

I'm thinking of building a cheap-ish computer but I have a few questions. I'll split them into separate posts to make things easier. Note: I won't be installing anything that I can't get to work on Linux.

Question about storage and swap memory.

I plan to install an SSD of maybe 128–256GB for the system files and a larger HDD for storage. I would partition the SSD so that I could install a few different distros without losing any installation. This way I can commit to some longer experiments before deciding which distro to use.

The question is: should I have the swap partition on the SSD (with the OS partition) or (separately) on the HDD?

And if I install multiple distros, do I need a different swap partition for each one? For example, if I install 16GB RAM, do I need a 16GB partition for, say, Mint, Debian, and Ubuntu? Or can I let them 'share' the swap partition?

Are there any additional security/privacy risks of installing more than one distro on the same SSD card?