I've noted that when he needs more dexterous bladework, he uses a one-handed grip suggesting that he studied Form II: Makashi and his opening stance in his "duel" against Luke on Crait seems to be a more aggressive variant as opposed to its more relaxed stance. And uses this when he wants to keep his opponents at a distance, something that Makashi is known for, whereas Djem So is all about closing the distance with dominating aggression.



As for why I say he studied Form I: Shii-Cho, when he deflects blaster bolts, he uses wide sweeping slashes to swat them aside, whereas a practitioner of Form III: Soresu or Form V: Shien would not be so wasteful in stamina expenditure. But I think he never expanded beyond blaster deflection with this Form since he's never seen using its sequences, though it could be argued that it can be mistaken for Djem So if he used wide hacking cleaves, like the Falling Avalanche technique.



Additionally, I think that some dedicated Djem So practitioners forget that it's equally used for stonewall defense and counter-attack; with this in mind, they just bombard with heavy cleaves. I Kylo Ren's case, he's emotionally unstable, so his technique might be equally erratic which might have given you the impression that he studied Form VII: Juyo.