i usually edit them (manips) in capcut which turns it into a video then i go to ezgif.com and convert it into a gif there. i dont really know how to use photopea unless its for psds so i found that for me personally this was an easier way to go about it. hopefully this helped a little bit? <3
photopea is the best way to do it, there’s a lot of very easy tutorials you can follow either on tumblr or yt! either way if you need any extra help feel free to message me