In my trials the application start could be speeded by unpacking in to a directory home and creating a personal starter.
One example. LibreWolf
The appimage takes a couple of seconds to start on my i5 quad core system, unpacked it starts in an instant.
The waiting time is due decompressing the package.
How, just run the appimage with following –appimage-extract.
Caveat if you have a rarity, “very old appimage” the command might not work.
Being able to examine the contents of an appimage and remove anything unneeded or unwanted is also useful.
In case of LibreWolf I removed the hidden form autofill and screenshot plugins as well as pingsender, the latter
(claimed) unused unless explicitly allowed, removed–for sure no pinging to mommyzilla.