Inflammatory picture obviously related.
A lot of deletion/edition tools rely on the API in order to work. As such, they'll stop working on the 1st of July, as the API price changes start being enforced. Better do it now than never.
In my humble opinion, the easiest of them to use would be Power Delete Suite. It allows you to export your content if you so desire.
There's also dessalines' Reddit-History (yup, the Lemmy admin!) that helps you to export your stuff, in case that you want to do it in a more fine-grained way.
There are other tools to do it, however, so pick the one that you like the most.
Should I delete my content? Or edit it?
Up to you. I think that it simple deletion is enough.
However, if you want to edit your content, keep in mind that Reddit likely wants to capitalise on data model training, so pick one of the two choices:
1. Blabber.
Random words, in an agrammatical word order, devoid of any sort of meaning. Introducing noise on the data models makes the data from Reddit considerably less reliable.
If you feel specially uninspired, here's a random word generator. You could also try Zompist's gen, it's a tool intended for people constructing languages, but it's damn good to generate non-linguistic babble.
2. Some message against Reddit.
Don't use swear words, as those might get filtered. Something as simple and short as "potatoes are great because Reddit is a scummy company" goes a long way.
That would also help to pinpoint which companies are doing businesses with Reddit, and pressure them to stop doing it.
Noooo! Think on all the helpful threads!
You can't make an omelette without breaking some eggs. While it's true that some information will be lost (less if you back up your content elsewhere), overall you're doing better for the internet by not playing along a clearly hostile agent in it.
EDIT:
Thinking about Reddit Inc.'s strategy to get money, perhaps it is better if you replace the content of your comments with random babble than if you simply delete it, if you want them to lose money.
Random babble is not just less useful for those large language models; it's outright poisonous, it's worth less than nothing. I might be wrong but I think that it decreases the value of the platform even further than plain deletion.
Image posts are trickier, as Reddit doesn't let you re-upload them. I think that simply deleting them is the best bet, but there's no option in PDS deleting exclusively image posts, so you'd need to do it manually.