The red glow around windows can be changed in: Settings > System Settings > Workspace Appearance > Window Decorations ; you'll see a list of windows decorations, you can choose a new one, or scroll down to "Oxygen" and click to highlight, then click "Configure Decoration". The red color is under the "Shadow" tab. You can change it to any color you like.
Disabling "Various Animations" from above may fix your task bar auto-hide problem too but if not, it's somewhere in destop effects I'd imagine.
I'm not sure about your login screen. Are you using multiple users? You shouldn't see a KDE login screen if you're booting properly.