- Where I live SSD storage has become very cheap and the price premium for going from 200 GB class SSDs to 500 GB class is insignificant. So I’d suggest going with an entry-level 500 GB SATA SSD like the WD Blue in the first place.
- Following from that my opinion is that SSDs are big and durable enough to put swap on them without an issue, assumed that you won’t be swapping constantly. This heavily depends on the amount of RAM in the system. My old-ish laptop only has 8 GB of RAM so I run it with an additional 8 GB of swap file on the internal SSD. My main PC has 32 GB of RAM and I run it without any swap. In any case you’d want to put swap on the fastest storage possible so that your system stays somewhat responsive during swap usage.
- You can share swap partitions without any issue since swap is usually wiped/overwritten on boot.
- Every OS on your system can read any data from any disk/partition. If you want to have secure separation you need to encrypt the data.
On the contrary it’s better to get a bigger SSD since the writes for swap usage get distributed more evenly across the larger memory pool. Modern SSDs can take a lot of writes before degrading since their controllers are very smart. USB drives get worn out a lot faster since they lack redundancy in storage and good memory controllers.