The more important part for privacy: Mail address is optional, and IP addresses are not stored in the database. A correctly configured instance (at least for EU legislation) also will not log IP addresses in the web server - with that you can have profiles that can't be tied to an actual human, and you don't have location and movement data.
The data deletion is pretty much a nice to have - it's on the level of the Exchange feature to recall Emails: Sure, you can ask nicely, but outside of your own server pretty much nobody will care. Lemmy is federated over multiple jurisdictions, so even with full deletion implemented there'll almost certainly be instances which will ignore the deletion request - and it will be completely legal for them to do so. More important is education about what you publish, and a basic understanding of the technical and legal realities you'll have to deal with if you later decide you want that information gone.
I already had that discussion with my 6 year old when she wanted to publish some videos - and she understood the problems quite well.