I feel like this is a dumb question but bear with me. When I install something I like to look at it in-game to see if I like it enough to actually keep it. Problem is I have heard time and time again that you should never ever delete a custom food once you have installed it (although I never really understood why.) So if I were to move my main hood to the desktop and create a test hood to look at the custom food (sims will cook it and eat it) and then I delete the food I don't want to keep and delete the test hood, would that be okay? Thank you.

If the food was just installed and looked at you can delete it so long as you delete the sims memory of making and eating it. Custom food in for some time may become a sim favourite food as well as leave memories of making and eating it. or use a test hood.

Yes, it's fine to try in a test hood. In fact, I keep a hood just for testing stuff.

Custom foods usually leave memories when a sim learns to make them and they also can become a sim's favorite food (the dish that a sim gets when you choose the "Chef's choice" in a NL restaurant), that's why deleting them can lead to 'hood corruption. If you want to avoid it, you should delete the memories related to the custom food from all sims and also clear their favorite food token linked to the custom food (one of the options of the Batbox does it). If you will delete the test 'hood afterwards, I guess 'hood corruption isn't a issue, so it's fine.

I know a few custom foods that doesn't leave memories (those, for instance), I was wondering if it's possible to edit other custom foods in SimPE in order to remove that memory feature.

From what I understand, deleting custom food won't corrupt a neighborhood in the same way that deleting sims, putting occupied lots in, deleting multi-PT mods, etc. would. It more just messes up any sims who have a token or memory for that specific food (regarding "burned $subject," "learned to make $subject," favorite foods at the NL/OFB podium). Sort of in the same vein as if you delete geneticized/townified CC. It'll mess stuff up, but it won't break the game and everything that gets messed up is fixable.