As stated - It’s really all trial and error and finding what works for you. One person’s bad tension is another person’s good tension, one person’s too thick is another person’s too thin, one person’s good for slack is another person’s bad… And so on.
Twisted thread: simple concept but with loads of variables.
There are different threads for different objectives. Best I can offer is echo what has already been said - try as many as you can to find what works best for you. I like dual duty XP.
I have a weird sickness - I love making string, even though I find it’s cheaper and less time consuming to just buy string.