Thank you for your very helpful post. I agree that an aimbot is maybe a bit too ambitious of a first project. But, I will be content if this takes 6 months and I learn a lot. That's good enough for me.
I have found some success and good code examples. I would post links to those code examples, but I'm not allowed yet. Overwatch was indeed stopping CheatEngine specifically because Overwatch continued to function while my own simple scanner worked well. I'm using VirtualQueryEx and ReadProcessMemory to find my own name in the process memory for Overwatch. This is a very small but important first step. Next, I'll try to find the offset from the base address and begin exploring the memory near my own name in the hopes that the x, y, and z coordinates are in the same data structure and in close proximity. Then, if I can find the distance between player data structures of if they are part of some linked list, I can find the coordinates of other players too. If I start to have some success, I'll share my information in the Overwatch forum.
You seem experienced, so if you have any advice or links with respect to aimbots, please share and point me in the right direction. :-) Thanks again.