RE: Several Question for Memory Upgrade Dell 7567 and other stuff
1. Not with Dell, but the RAM won't carry the system warranty. Memory is user-upgradeable. While it's possible to use mismatched RAM, matched sets will perform best.
2. Could be virtual memory that's at fault, yes - particularly if you have a spinning hard drive rather than an SSD.
3. That's either the fan or a hard drive - the only two things in the system with moving parts.