I don't quite understand how to run services on Mac?

After on&off working on various projects, I have finally worked out a few things that are useful and stable. So I would like to have them running all the time. yay!

I did a bunch of reading on the subject and found there are about 100 different ways to accomplish this but I don't quite grok the big picture.

The native Mac way is using launchd. Also came across forever, Nodemon, cron, at, batch, upstart, entr, task spooler and some other things that aren't coming to mind.

I don't understand exactly what to do with these. Do you have to have a bunch of terminal windows open all them time? If not how do you see what's happening?

On the other hand, do you ever set something to go indefinitely and forget about it by mistake? I am concerned about setting things in motion and the results being so obscured.

Do you include cding to the directory where the repo lives in the script/plist file? or do you put every service on your path so it can be called from anywhere?

do you run services as yourself, create a new user/group for each, or something else?

I hope someone can understand the question I am trying to get at here. I get the broad concept but not sure how to implement.