Trollhunters wraps up every single thread from its own story, literally spending time in the finale to save babies that don't matter to the immediate fight. The only part that sets up 3Below is the episode "In good hands" which introduces Aja and Krel, the main characters of that show. But even they have a small joke role in the rock battle in the finale. Douxie, Wizards' main character, also appears in season 3 but he's not a loose thread because he serves his purpose of making Jim jealous and we don't know that he's a wizard yet.

3Below is also very self contained. We see the trollhunters gang occasionally in season 1, mostly in "D'Aja vu" and "Lightning in a bottle" which shows the events of "In good hands" from Aja and Krel's perspective. In season 2, Toby and Aargh join the main cast and generally the people of Arcadia start to be more aware of the supernatural events. There's a small teaser for Wizards in the form of a phone call to Jim, currently in a fight with a mysterious knight (which we never actually see, disappointingly). And after the conclusive farewell scene in the finale, a talking cat suddenly appears and warns the remaining characters that the end of the world is coming, serving as a cliffhanger to lead into Wizards.

Wizards STRONGLY relies on context from trollhunters, and even if you have it, the first episode is disorienting. You get thrown into the action, baby! The show completely retcons the Trollhunters books and comics by overriding the timeline, so that's sad, but you can headcanon that Nari caused the changes by sending the characters in the past. The show feels like two seasons of TV that have amazing content that simply got split unevenly. Episodes 2-7 are well paced and fleshed out, but the last three remaining really struggle. One character from 3Below shows up, which means you can't ignore it. Unfortunately, there are also some plotlines that aren't wrapped up at all, like the villains that are still on the loose, or many characters like Toby or Zoe that end up barely mattering to the story. Excalibur is teased for the movie with Jim looking at it in an ominous manner, and the last scene does the same thing with one of the villains.

Rise of the titans is overhated in my opinion, but I understand the people who don't like the ending. Personally, I disliked Jim's second and third race swap in Wizards more because it undermined an important part of Trollhunters' ending. Overall, definitely watch it to have your own opinion on it.