I've run the current edition for a group of 4 (in addition to some GMPC's, since I never actually get to play l5r)
Honestly, don't over-think it. The bolded portions are actual rules of the game, not just good Game-mastering or whatever.
Remember that narration always comes before dice rolls in this game. The players always chooses what stance/ring they're going to use and often they even have a choice of skills, but before they get their dice-pool together, they are supposed to narrate how they are using their ring and how the skill actually applies. (so no role-playing means no dice-pool) The GM decides if their narration is appropriate and how it effects the TN. In essence, the ring/skill is already a result of roleplaying, rather than being required for role-playing. One could argue that in this game, poor role-playing can get in the way of mechanics. Where the scene "slows down", it's more likely a result of the player/gm knowing the mechanics and trying to figure out how to narrate things to get the mechanics they desire, as opposed to knowing how to narrate things and trying to find the mechanics to make it work. If things seem "too mechanical", it's probably because the GM isn't really enforcing the rules.. However a GM should also try to help the players tell the story of their characters and some leniency must be allowed.. finding the balance is possibly the hardest part of the game.
Opportunities are easy. You can use them to add details to the story.. and they are pretty well open to interpretation after that. As I've told @Avatar111 in the past, I believe that situations in which "Opportunities are better than success" are far more rare than most people realize, and are generally the result of the GM under-emphasizing success. We talked about 2 examples.. one in combat and one in social conflicts. Many uses of opportunity in combat require a successful attack, but one use that doesn't is grappling/snaring. Using grappling/snaring, you can use several opportunities to give your opponent the "immobile" condition, but the only things "Immobile" does is make it so your target can't use move actions and can't switch stances. This condition can't actually resolve a conflict. It doesn't even make your opponent stop fighting for a turn.. and it only lasts one turn. On the other hand, getting successes to incapacitate your opponent effectively takes them out of the fight and, if they're the only opponent, ends the conflict at least for the scene. In social situations, "fanning the flames" has similar issues. It has interesting effects which are temporary, unpredictable, and don't actually end the conflict, but might draw it out. In actually resolving conflicts, success is king.. if success didn't make a meaningful difference to begin with, then the roll never should have been allowed. No roll means no opportunities so success/failure must matter in order to even have the chance for opportunities.
Finally (for now) Strife doesn't just come and go based on die-rolls.. it's pretty much what courtiers are based on.