I prefer to keep my data on my own machines. I have a freenas server and use syncthing to synchronise photos between my phone and the server, with a cron script to organise the photos into folders.
I'm also reading a book at the moment about the history of prime numbers. Both Gauss and Reimann were such perfectionists that they didn't publish (not archive) proofs they claimed to have. There is evidence they knew much more than they let on because it wasn't up to their high standards.
There are many source online that refute the "nothing to hide" argument, and they can go into quite some details. Suffice it to say, you have a right to privacy. If you wish for something to stay private (for example, to protect yourself from harm) you have that right. Whilst in most free societies it's seldom required, there may come a time when tyranny takes over. If you've already given up your right to privacy, you'll find few protections left. History has many example of tyrants that, given the data mining capabilities of today, would have probably caused even more harm and suffering.
Writing your own engine for your game means your game will take a lot longer to create. That's not necessarily bad. You might enjoy the process, revel in the things you will learn. If you want to make your game, and focus solely on why it will be "The Most Awesome Game Ever", you may get frustrated seeing little movement in development because you're too busy trying to get the engine to work.