I’m usually not a fan of putting desktop files in autostart, probably because I much more trust systemd service files, but if it works for you it works for you 
As far as I remember the autosettings, they are text files they need to be in ~/.config/PulseEffects/autoload, named as [pulse-audio-sink-name].json and contain the bit of json telling which profile you want to load. If you use flatpak, it should be in ~/.var/app/com.github.wwmm.pulseeffects/config/autostart/