The battle effects and numbers are called flying text. There's also pop-up text, but I don't know if that covers the other stuff you want to change because
I don't know what it does.
Enemy names and HP bars can be changed under display name settings. You can change the names to only display when targeted. The HP bars are either on, only on at <100% health, or off completely (there's no "when targeted").
Ignore the rest of my HUD, it's firmly in "It works for me and I can't be bothered changing it" territory.