Yeah, tbh it's something that is much better avoided preemptively. Once you're using that stuff there's not really any deleting it. I'm sorry to be the bearer of bad news. What you can do it contact the companies and tell them you want to wipe your accounts. They will oblige but not particularly helpfully. They're all geared towards keeping you using their services and using your data to their ends so customer service on this front is quite lacking.
There's some things you can do. I touched on closing yoyr accounts. You can also leave a descriptive note which will anser any questions LE may want to ask. Basically make it easy for them to wrap things up with as little effort as possible. They'll take that. If you have people you're leaving bwhind you can write separate notes if you prefer to separate certain things. Kind of obvious but mentioning it while we're on the topic.
LE can request you google file which will include search history, media posts, location history, how many pubic hairs you swallowed in your life time and of course your contacts and call history.
Similar situation with facebook, twitter, instagram, tiktok and all the others really. It takes them a period of time to delete yoyr shit even after sending an official request so it's something you will want to do a good bit of time before ctb.
I think with icloud you can clear it out and give it some time so that it's wiped from any servers they have. Not sure how long thst takes.
Like I say, if you make it easy to wrap up they may never bother accessing your phone/devices or online accounts. They will take thst stuff just in case there's an investigation but will return it untouched if they can wrap things up without doing so. They have limited resources so won't go to those lengths if they don't need to. Usually returning your stuff to your family once case is closed. If youf family/loved ones will be likely to put high expectations on LE then you may want to go ham on clearing out beforehand.