Plan for workflow efficiency strategies

Great course, as someone who is quite new to After Effects, this definite helped a lot. Here I have some of the things I have incorporated into my own projects, as well as a few questions all the way at the bottom.
Hope it's not too much, tried organizing it as well as I could :)
Questions
I don't know if it makes any difference, but I don't have a lot of storage locally, using an external drive for Disk Cache location won't be any problem, right?
As I wrote on page 1, pre-rendering individual compositions as PNG sequences did not help improve performance when already inside a composition, Am I not supposed to pre-render compositions inside of compositions, or did I possibly do something wrong?
I also experienced the render time disappearing and bugging out whenever I wasn't moving the Current Time indicator, is there any fix to this or is this just Adobe bugs being Adobe bugs? I updated to the latest version.