Revan's Lightsaber form
Revan, Celebrated as a Jedi Knight, dreaded as a Dark Lord Of The Sitb. Saviour, Conqueror, Hero, Villain. In the end Revan was all those things and much more. He is considered by his master, Kreia, to be the heart of the force. Whether you loved him or hate him, Revan is still a very hot plate that everyone wants to try, he was skilled in force lightning, Telekinesis, Force grip, Force choke, Force crush, Force healing and could even conjure up a force storm as well as use the force to rain down a hail of asteroids at his opponents, in his holocron. He is stated to know ancient sith techniques some of which Darth Bane considered too dangerous, he had great knowledge of tutaminis and could open himself to both sides of the Force. Revan is - with out doubt, the most powerful Force user of his time, having knowledge of the dark and the light.
however with that said his lightsaber from has never really been elaborated, which is very foolish in my opinion, so I will take upon myself to explore Revan's form, all of this will be based on Revan's personality(which is very common IMO. Dooku-Makashi Obi-Wan-Soresu)
Revan was a powerful warrior and swordsman, he was able to defeat Mandalore The ultimate who was considered the strongest of the mandalorians( AT THE TIME) and the legendary echani General Yusanis. Who challenged the dark Lord. OK judging from this we can safely say revan was good in one V one combat and was able to stand against Yusanis' double blade so he could've known Ataru or Makashi. During his retraining as a Jedi, Revan Remained a powerful duelist, having defeated the Jedi Juhani who was primarily a lightsaber duelist, he would also defeat The Headmaster of the Sith academy Uthar Wrynn who wielded a double lightsaber and his shoto wielding apprentice Yuthura Ban, and took on the entire korriban academy. Having said all of that I believe Revan was skilled in Shien or Shii-Cho both of which would make a lot of sense, since revan being a tactical and calculating fighter would not weaken himself I think both forms could easily apply to him, IMO. He was able to defeat his old friend Malak who was considered one of the best duelist of his time, while he was being powered by the dreaded Star Forge, as well as Bastila under the demoralizing effect of her battle meditation. This heavily implies Revan was skilled in a one on one lightsaber form, like Ataru or Makashi which could clash with Bastila's more aggressive and untamed style and malak's Ferocious yet focused form. He was able to hold his own against the true sith emperor while under the effect of the drug, which would ultimately lead to his capture and Meetra's death, he would later fight against a imperial strike team, once again his battle with strike team shows that he might know Shii-Cho or Shien. Form what I gather Revan Knew Shien and either Ataru or Makashi as both form were quite common during the Jedi Civil, I however, don't believe revan would learn Niman considering he was not the kind of Jedi to choose weakness over power IMO.