About the second one, performance should be crucial everywhere, if some application eats all the resources then I can't have other applications working in the background doing their stuff. That's the problem with i.e. "modern" communication apps (I'm talking about you, slack) where my four core CPU is on it's knees when doing simple things like switching the team or even channel, not mentioning starting the app itself. Another one is when I'm on the Google Meet chat, my browser eats 80% of CPU, I can't do anything reliably in that time, running anything makes chat to loose audio, lag a much, etc.
Going back some years ago, I was able to run Skype, AQQ, IDE, Chrome browser and Winamp at the same time on archaic (in today's standards) i3-350M and 4 GiB of RAM.