Low latency, it's a kernel made specifically for, you guessed it, low-latency applications, such as gaming. As for where you get it, on Ubuntu I don't know as I'm an Arch user. (btw)
I am in love with the KDE System Monitor widgets. They were, of all things, what truly cemented the Linux switch for me.
I used Aquasuite on Windows to control my watercooling, and it can set up a vast amount of widgets on your background for easy monitoring of temps and other values. It will not run on Linux.
The KDE widgets give me basically the same experience, although missing a few things. It's enough that I'm happy with it, and I can check temperature and flow rates at a glance if something starts acting fucky.
I've used xfce and honestly KDE has a lot more customization potential. This is really helped along by the massive community compared to xfce, which means you get a whole load of potential widgets for your panel and desktop
You see the thing about kde they nailed their motto "simple by default, powerful when needed" the thing is the path from simple to powerful is an obscure one
Can you show or write what you did with the panel? Is this the default one? What widgets are active on it? Other customization specifically aimed at the panel?