Late to the party I guess, but I think there’s a lot of misunderstanding about the ethos and principle of classic play encoded in these questions. Not that that’s bad, I can see where it comes from, but it strikes me that a gentle suggestion or two might lead to a better experience with classic style games.
I’ll also say that to give full answers to some of these would get into essay length maundering, and who has time for that? I’m gonna be quick and messy - so assume some nuance.
(1) THE DISTINCTION BETWEEN IN CHARACTER AND OUT OF CHARACTER RP.
Two issues greatly effect the degree and nature of in character decision making in a classic, puzzle focus game, congenality and success.
In older games characters have no narrative control at a meta level, but a great deal at the diagetic one. That is the players have no input into the setting or its actors, but the characters aren’t constrained to any specific course of action either. What this means, especially combined with high lethality and deadly risks/puzzle is that acting in character is great until it comes up against risking your fellow player’s characters.
Yes your barbarian might hate wizards, but rushing a neutral Wizard King faction leader while the rest of the party tries to negotiate is bad play. It will likely kill the entire party (ethos demands that the GM is a neutral arbitrator, and should not intervene on behalf of PC survival) and even if it won’t it will set the narrative down a specific course - war with the Wizard King. That’s just not a cool thing to do with fellow players, force them to follow your character story. It’s not congenial. Likewise, emphasis on intra party conflict is discouraged, the world is tough enough for the whole party together - don’t split it.
This gets to the issue of success. Since many of the key challenges in classic play involve players unpuzzling things It’s detremental, and avoiding play, for a player to decide not to engage with a solution because thier character is too dumb, or incapable of offering it. Yet there’s absolutely space to reject puzzle solutions for in character moral reasons “my character wouldn’t use captured goblins as trap detectors”, but there’s sort of an expectation that the player won’t use in character traits to avoid engaging in play entirely.
(2) PACING
Pacing in the narrative sense is not a concern, to try to provide it would almost certainly require damping down player freedom through illusionism, railroading or similar disfavored techniques. This is an intentional trade of to focus on player decision rather then narrative form.
Design for locations and setting is the only tool for pacing, but can go a long way especially with campaign clocks or event tables.
(3) PLAYER AUTHORED MATERIAL
Player created material is deeply part of classic play. Most of the iconic D&D classes, starting with the Cleric, come from player desires.
However, the GMs and player roles are fairly well defined and the ethics of classic play frown on unprompted player creation. GMs often request content “What God does your cleric worship?”, “What does your wizard’s magic missile look like” or “What distant land is your PC from” for example, but this sort of thing generally stops at mechanical effect. E.g. you might say your cleric worships “The Fire Bull”, but your GM and fellow players will take umbrage if you insist this means you get a special charge attack and immunity to fire. Now your GM might be inspired and make a subclass for you or add in your temple as a faction, but that’s not expected.
On the other hand there’s a tradition of player ingame creation: spell research, item creation and even classes (You charmed some goblins, made them henchmen and now want a goblin as a replacement PC) - but again this is almost always through collaboration with the GM.
Okay these are getting long. I will do the rest after work.