Put me in the camp that doesn't like low-is-better mechanics, but not to the extent that it would prevent me from playing a game I otherwise liked. Only mentioning it because you said it's the first time you've seen that complaint.
Doesn't Pendragon use low rolls? (It's been a while; I may have that wrong). EDIT: Yes, I just checked.
And coincidentally, I forgot it uses a mechanic similar to what I suggested...in that other warm & fuzzy thread...would have been apropos for Conan: traits come in opposing pairs ("lustful/chaste") that always sum to 20. "Civilized/Savage" anyone?
Yes Pendragon does use roll-under rolls (on d20 as aramis erak correctly pointed out) - and it has the opposed Passions system. Although if you try to define 'barbarism' then a mixture of a few of those opposed passions would better represent it, and in fact the powers of Christianity and Paganism which may visit the faithful in that game are linked to achieving high levels in three relevant traits - such as Chaste/Lustful, Modest/Boastful or Temperate/Indulgent. I imagine Civilised/Barbarous could be dealt with similarly using that system.
If you like that sort of thing, then the Mythras System has a passions system based off percentile dice (d100 like RuneQuest and Pendragon as you mention) which doesn't do opposed rolls of two, but which has a similar in-game effect (if you make a passions roll against Love of Family for instance, a success can boost your other skills relevant to defending them for instance, or a Loyalty Liege Lord replace your failing Willpower as the roll you use to resist magic manipulating you to betray.
I like the Mythras system better as it is less binary and more influenced by the player than the Pendragon system, which can really hogtie you sometimes and even lead to unavoidable character retirement or death.
For depicting the world of Conan, the Mythras system would have been fine, although passions running high is only a part of the genre (and this element of it) insofar as you might expect in another type of dramatic story, so I am not sure it is a
necessity.
Where the Modiphius Conan shines is in the Resolve and Trauma area I described, and in that, your ability to act and the consequences to your willpower, morale or state of mind can be just as impactful as passions in Mythras. They are different though.
There is of course also the issue of your character's Nature trait, which impacts Fortune point regain and the expected approach to stress/challenges taken by the character wrapped up in that. I didn't go into any real detail on that in my review but it would figure in the portrayal (both narratively and mechanically) of your character and their chance of success and failure linked to being true to that Nature.
