I don't have any sort of list, but I've been through a handful of apps and most of them have had the option to preview before posting - although the button icon doesn't always convey what it does very clearly. If there are any buttons you're unsure of in your Lemmy/PieFed client, you might want to try searching for communities named "test" where you can post junk posts just to make sure things are working as expected. You can play around with your app's buttons, and any posts submitted accidentally will be ignored (or at worst joked around with).