Questions That Need Answered
 

(Sorry for possibly asking already answered questions, crossposted from Reddit)
This might be a bit long but I need clarity. (questions at bottom for people who don't care) For some backstory, I am looking forward to getting a project car. I have decided to pick up a 1995 Honda Civic Hatchback DX. Seeing the aftermarket abundance of this platform is amazing, but I have one problem. I know nothing about cars. I've been doing my research on my own, but I have plenty of questions that need answering.
1. I see a lot of people talking about car tuning (fuel and air ratios and whatnot), but not explicitly when I should do that when upgrading my engine. I heard it is unsafe to run a turbo or larger fuel injectors without a tune, so how would I know what to change when no change is needed?
2. When engine swapping a car, how do people know what wires go where? I familiarized myself with all of the engine components, but I can't figure out the wiring for the life of me.
3. Again, when talking about engine swapping, there seems to be a number that everyone can agree on when it comes to the amount of power the engine can take. However, I see some people running way over that amount with seemingly no issues at all. Is there a way to increase the amount of horsepower without risk or do they just not care too much about the longevity of their car?
Thank you for anyone who takes the time and listens to my questions, that I can't seem to find answers to.

I'm not touching this and my suggestion is that you don't either.