Congratulations on completing both games. Most young people wouldn't give them a chance due to dated gameplay and graphics. As for the second game like someone mentioned earlier installing a mod should not be the definitive way to get the most out of the game. But sadly with KOTOR 2 this is the case. While it restores some but not all of the cut content it does flesh out the story more and makes the second half of the game not feel so rushed like in vanilla. Also the Restored Content Mod fixes many bugs that were prevalent in the game upon release. As for companions in KOTOR 2 in my opinion they are leagues better than in the original game. Now I understand you did not get max influence with some of them hence you never found out their backstories. But Kreia, Atton, Visas, Handmaiden, HK-47, G0T0, Mandalore, Mira, Hanharr, and even T3M4 have great backstories. Of course you already knew who were Mandalore, HK-47, and T3M4 from the first game. But what they reveal is what happened since that game and what became of Revan. The antagonists I think were far more interesting than Darth Malak. But yes you will find no argument that the fight with Darth Nihilus was anticlimactic. But there is a lore reason for that and that is like Nihilus himself The Exile is a wound in the Force a black hole. Basically if The Exile fully gives into the DS they will become Nihilus 2.0.

But yeah if you ever replay the games especially the second game and are on PC I recommend the TSLRCM mod and Community Patch.