One of the biggest tasks of creating 5e modules for Howard's Conan stories is to make sure the Player gets to play as Conan along various parts of his development. One of the first problems is balancing Conan against other NPCs and Enemies, which ultimately will require to bend some of the Character creation rules so that the stats and abilities for the Conan Character match up with what he is capable of doing in the stories. My goal is not to be bound by 5e rules but to use 5e to recreate the characters and stories as much as possible.
The easiest approach I can take is the same as Howard, starting with Conan as King of Aquilonia and at the end of his adventuring days. Starting the player at level 20 and with full abilities in the first module, Phoenix on the Sword, will give me a great template that I can use to roll back levels for various stages of Conan's development.
After pouring through the Player's Handbook, I came up with a combination of classes that I think best covers a fully developed Conan in 5e. King Conan would be a Barbarian 12 / Rogue 5 / Fighter 3 at maximum level 20.
The Core Ability Stats of Conan
Before I start breaking down Conan's 5e classes, archetypes, and feats I have to start by setting his Ability Scores. One of the problems I ran into was using the standard techniques of determining ability scores to recreate the literary Conan. Conan's numbers can't be arbitrary. Rolling for them or spending points to set them at level one tend to leave Conan with stats below what he would have in a typical Howard Story.
What I kept coming back to is contrasting Conan with character classes built by traditional 5e rules in a traditional 5e party and setting. If I put Conan into a group, how would he compare and still have the flavor of Howard's creation? If I were to take this build and put him in a party of level 20s and run an appropriate adventure, Conan would still have to be Conan.
You can find a variety of "Conan" builds online that use traditional Ability Score setups to create the character, but none actually capture the depth of the character as Howard wrote him. In the strictest sense, Conan's primary stats are obviously Strength, Dexterity, and Constitution. In fact, these three traits are the most commonly emphasized by Howard, especially in combat.
Where most builds fall short of a true Conan are the dump stats. Often Wisdom, Charisma, and Intelligence take a hit, leaving the character with the noncombat abilities of an ignorant, witless social boar. Howard's Conan is far from this.
The problem with dumping Wisdom
Wisdom in 5e governs Insight, Perception, Survival, Animal Handling, and Medicine Checks. The biggest issue with dumping an 8 or 10 in this and calling the build Conan is that Howard's Conan, being a true barbarian, would be very proficient in Perception and Survival. At the very least any Conan build would be proficient in both so that the Proficiency Bonus could be used to augment a low score in Wisdom.
The problem with dumping Charisma
Conan is a charismatic character. Throughout the Conan stories, his Charisma is often pointed to as he frequently assumes leadership positions by being well-liked and respected by his peers. Charisma, if anything, should be the fourth highest stat for any Conan build.
The problem with dumping Intelligence
Probably the most common dump stat of all, Intelligence. Popular culture might reduce Conan or barbarians based off him as a dumb brute in loin cloth swinging a massive great sword, but Howard wrote the character quite the opposite. Conan was a highly intelligent character. He knew many languages, and learned new ones very quickly. He could read and write and could decipher code. He was a great strategist, and as a King a great ruler whose ideas led Aquilonia to flourish under his reign. Far from ignorant, Conan always seems to know a great deal about History and Nature, in the 5e sense. So again, dumping an 8 here would drastically change how the character would play.
At level 20, I decided to set the stats outside of the regular character creation guidelines. For earlier levels, I will probably roll back some stats a little to show a youthful Conan. But for the King Conan stories, at level 20, he will be at full power. Especially since the grandest and most epic of his adventures, Hour of the Dragon, occurs while he is a king.
Comparing his stats with stats for NPCs and Monsters in the Monster Manual and DMG, I set Conan's stats as follows.
Strength is set at 18. He needs to be at the top end for medium sized humanoids and pretty competitive against large sized humanoids, but going a full 20 would seem to be out of contrast with most creatures in the MM.
Constitution is maxed at 20. His stamina is always described as nearly endless, and in most stories the very thing that sees him victories is not his superior strength or dexterity, but his stamina and resilience.
Dexterity is not quite maxed, but is set at 17. Conan was a very agile character, and more importantly a very stealthy one.
Intelligence is the one true dump stat. I felt that 10 would still allow the character to be true.
Wisdom is set at 13 because it influences some pretty core abilities for the Conan character out of combat. Charisma is set at 14 for the same reason.