Patches Are Applied in Main firmware, and elves starts Automatically or manually from FS.
Elves use more heap than patches and make the phone unstable.
You can apply as many patches as you want, but make sure that no patch causes conflict with another patch.
You can have as many elves as you like, but always taking care not to exceed heap, so there is no reboots and instability. Also, you should ALWAYS have updated library and Dyn_const.bin to avoid reboots.