It's not just age, plenty of people find 2 spaces hard to read. Thus the only logical choice for indentation is tabs. That way every reader can pick the size that is good for them.
I only can use it on personal projects, as most places I worked in use spaces.
The limit on what constitutes a reasonable line length is a bit subjective but I'd say that well written code rarely goes above ~120 or so. Depends a bit on the language, some just have more boilerplate than others. But instead of making that a hard limit I'd warn above that number so actual people can decide if it makes sense there or if a rewrite is in order. Auto-formatting is great and all, but ultimately a human should have the last decision.
Though if you force me to pick a value, then it's 4 because that's the sanest choice for like 95-99.9% of all people.