Every drive can fail at any moment. Even a brand new one. It is just a bit less likely than having a decade old drive fail.

If you care about your data make sure you have backups. 321rule.

Yes, you can use a “NAS” drive pretty much like any normal drive. This is an SMR drive so not even a NAS drive to begin with.

If you do not have backups pay a professional to recover it. Yes, this is wildly expensive but tinkering yourself can make recovery even more expensive or outright impossible.

You want to move your drives to your mainboard because a lot of those cheap adapters suck. Unreliable and they can buckle under load. Can be a PITA.

If there is performance to gain depends on how accurate your information is, what drives you use, and how.