I found an awful bug that annoyed me to no end. Popups \ confirmations (see screenshot for an example) would be slow showing up.
After messing around a lot I found the cause, and that is Pulseaudio which due to some bug caused a huge delay when the popup is loading, especially if the popup is assigned to play a notification sound.

I solved it like so:
1. Open ~/.config/pulse
2. Delete everything
3. Open terminal
4. killall pulseaudio
5. click on the volume icon to restart pulseaudio
6. Change the volume but do not touch device settings, do not disable devices, or you will trigger the bug again

Another bug that will reappear if you do this is the one related to not being able to unmute notification volume. There is an open bug report but I can't find it atm (will update with a link). To solve that you will have to unmute system sounds from another audio manager such as pavucontrol.

Anyone has any clue on what could be causing this? Also, maybe I'm being stupid and this is not possible, but is there any way to delete pulseaudio and use pavucontrol instead? If I try to remove pulseaudio it says that I need to remove a million packages related to the desktop environment and I know that if I do that I will break my system.