His Force abilities are well in top 10 of the mythos. His feats, his potential at youth, his advancement rate, his variety of skills, mastery over the Force he demonstrated and many more. I have him below Plagueis without a doubt, but honestly above Krayt or Talzin. The guy is a complete monster as far as the Force goes, and it's not because of the magnitude of feats only, as I mentioned above. I have no reason to believe his power would shrink in a Force only "fight". He may suck at using these abilities in combat, which is understandable; using the Force within fight is a very different set of skills, which requires good combat skill at first, if only to be able to get that one second break in a duel for a good Force attack.
Still, he never demonstrated the ability to call upon that power within direct combat besides fighting leviathan, which is far different from lightsaber dueling. And as far as his actual dueling abilities go, he's ambiguous at best, and sucks at worst.
Quote putting him in the ballpark of Kyle is elevated as "Kyp=Kyle" recently, which is absurd. Luke loosely thought mid-fight that Gaalan would give a good fight to Kyp or Kyle and probably win over Cilghal. But guess what? Gaalan can give a good fight to Kyle and still lose everytime. He can also give good fight to Kyp and win everytime. It was a very loose statement from Luke, so it especially shouldn't be taken as some hard mathematics lol.
His showings against Yuuzhan Vongs are good, definitely. But nowhere better than NJO Jaina, equal at best, and NJO Jaina lags behind the true top of lightsaber combat. And I'm not talking about the Slayer, as I think it has more to do with Kyp being surprised and fighting a completely new Yuuzhan fighting style. The same as with the first Jedi fighting the Yuuzhan Vongs at all, so I would never use Slayer fight to put Kyp down. But he just doesn't have any showings to elevate him above NJO Jaina. Stalling her when she was mentally damaged is his best feat I guess, and even if you take away Jaina was far from her top mental capacity, Kyp's ceiling is still NJO Jaina.
That's why in Force only fights I will favor Kyp over almost anyone in the mythos sans a few characters. But as far as regular combat would go I would never have Kyp beating Kenobi or Maul in any manner.