I’ll provide some insight on Porter Engle since his wookiepedia page is incomplete.
-He is considered one of the strongest Jedi of the High Republic era (a comic cover states he is the best duelist of the Order, although it’s probably an hyperbole since Yoda is around)
-His fighting style is peculiar. He wields two lightsabers, however he uses the Force to make one of them levitate and strike from different angles (similar to Kreia). This makes him pretty unpredictable, especially if you have no knowledge about it.
-He single-handedly challenged a mercenary army besieging a city. While being surrounded by the enemies, he used one hand to hold his lightsaber and deflect blaster fire from dozens of mercenaries, while with other hand he used the Force, lifted an enemy tank and crushed it mid-air (Starkiller-style)
-He moved so fast that general Veiss, an expert Jedi killer, couldn’t even react to him.
-He is so precise at deflecting basket fire that he disarmed 9 mercenaries, all at the same time, by redirecting their fire back at their weapons
That’s about it. He doesn’t have many feats against other duellists (besides beating a random Jedi master during a sparring session) but I’m sure this guy will prove to be powerhouse at least comparable to the likes of Maul, Kenobi and Vos.
You did a great job summarizing some of Porter Engle's feats from Phase II of the High Republic, but you left out some of his Phase I showings.
In Light of the Jedi, Porter Engle, Loden Greatstorm, and Bell Zettifar are ambushed by "mole mines," explosives that burrow through the ground at great speed, then pop up a meter into the air right at the feet of their target before exploding in a horizontal ring of shrapnel and fire. Bell barely managed to survive four of them by launching two into the air with the Force, slicing a third in half before it could detonate, and impaling the fourth before it could emerge from the ground. Loden launched all of the ones that came at him into the air to detonate harmlessly long before they could reach him. But Porter's display was the most impressive.
"Porter was in a low crouch, his lightsaber out and lit, a bright-blue blade he held in a reverse grip.
He was simply slicing the mines in half as they popped out of the ground. One after another-the maneuver Bell had performed just once and didn't even understand how he'd managed, Porter was doing again and again. The expression on his face never changed. His blade flashed, and the metal fell, and he remained untouched.
Both Bell and Loden were transfixed. They were both good swordsmen, and Loden even had some claim to being great. But this was like nothing they had ever seen. Not at the Jedi Temple, not from Master Yoda or Zaviel Tepp, or even old Arkoff. Bell couldn't imagine what it would be like to face Porter Engle in combat."
Then in the High Republic Adventures, Porter Engle single-handedly wipes out an entire Nihil Raid team, consisting of (by my estimate) at least a dozen Nihil, and half a dozen Nihil scav droids. Nihil are incredibly dangerous to Jedi in Phase I, due to their reckless, underhanded, and borderline suicidal fighting tendencies. In most Phase I books, it only takes two or three Nihil to be a match for typical Jedi of the era. But Porter Engle defeated a whole raiding party of the marauders single-handedly, with absolute zero displayed difficulty. And at the end of the comic, he heavily implies that he's pretty much single-handedly filling the prison towers of Starlight Beacon with all the Nihil he is capturing.
Regarding Porter Engle and his comparison to Yoda, it's worth pointing out that Yoda in the High Republic isn't yet the Yoda we see in the Prequels. In Phase II, Yoda is described as "middle aged" and just coming into his wisdom (in the novel Cataclysm). So it's possible that Yoda, while still one of the strongest Jedi of the High Republic, might not yet be as skilled of a swordsman as Porter Engle at this point in time.
With all of that said, I'm genuinely not sure who wins here. Porter Engle is at least spoken of in the same caliber as Yoda in the High Republic, and may even be his better. But Yoda isn't yet the Yoda we see in the Prequels, the greatest Jedi of all time up until that point. Quinlan Vos being able to contend with, and even beat Count Dooku, puts him in a similar standing (considering Dooku is able to roughly match the skill of Yoda).
If I had to pick a victor, I'd argue it's probably Porter Engle. Not because he's a better swordsman than Quinlan, but because he is more consistently shown mixing Force powers in with his displays of lightsaber skill, crushing scav droids while simultaneously deflecting blaster fire, crushing tanks while defending against an actual army, or even dueling with one lightsaber in hand and a second lightsaber guided by the Force. Even if we consider Quinlan Vos to be an equal swordsman to Porter Engle, I just don't see how Vos could defend himself against Engle's more masterful use of the Force while also keeping pace in a heated duel.
Thanks for the detailed answer, my knowledge of phase I is pretty lacking. Yeah Engle’s implied to be extremely fast and skilled. From that paragraph you posted it sounds like even that Arkoff is more skilled than Yoda in saber combat (“But this was like nothing they had ever seen. Not at the Jedi Temple, not from Master Yoda or Zaviel Tepp, or even old Arkoff”). Guess Yoda was a very slow burner despite his immense force potential, I’ve assumed he should already be in his prime by this time since he is 600.
Not sure if Porter’s force powers are “that” strong, since in the comic I read it’s implied that his “sister” is the more attuned to the force of the two while not being great at saber combat. Like they always say that they complete each other, making up for their weaknesses, so maybe while Porter is surely strong in the Force, he is not as much as in the lightsaber combat department.
Anyway I really like his fighting style and he’s already become one of my fav Jedi from the high republic era