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You’ll lose all your local data as the bootloader gets unlocked, so back them up.
Tutorials on modding phones, from my experience, are fairly obtuse despite the process itself usually being rather simple and straight forward.
If you want to go as privacy-oriented as possible, you’ll likely pick a vanilla system (that is, as close to AOSP, “Android Open Source Project”), and will often be on the lookout for software that is either DRM-free (no dependency on 3rd party software), or open source / FOSS (“Free and Open Source Software”). Also VPNs to mask your online usage may come with their own set of cobsiderations, like some sites breaking, some others considering it ban-worth, and others setting prices, languages, etc., to a given region.
If anything can be salvaged, I’d suggest backing those up, and then proceeding to make a fully fresh install. That will ensure you don’t come across issues inherited from the previous blunders, and also, I think, will give you the chance to take the same steps, but wiser than before, and so able to avoid the issues you either caused or came across. (Also something I’d recommend maybe around every 1~2 years, precisely because of being able to restart but wiser)