I don't mean to be pedantic, but what you're referring to is the "persist" partition - you are correct, though; messing with this will break your Widevine L1 and it's nearly impossible to get back. This partition also contains all your sensor information (accelerometer, gyroscope, proximity, etc.)
Though it can be restored using OrangeFox recovery, messing with it is still a bad idea and, like you said, will definitely break Widevine L1 with no way of restoring it.
Last week I waited before I downloaded, and the speed was quite good. WIth limited bandwidth from the servers, and everyone rushing to get their new ROMs, there is always a lot of congestion to start with. So if you're not in too much of a hurry, it is better to wait - it will be faster, and there will be no drops.