I’ve dabbled in trick room myself, and it’s pretty cookie cutter this gen IMO. Magearna is the only thing ABSOLUTELY mandatory, but you’d have to have a really good reason not to use Mmaw, Alowak, and Uxie. Mmaw can be substituted for mega camel with some success, though mawile is superior in my opinion. Alowak has really great type synergy with the double steel/fairy core of mawile and magearna so you really can’t pass it up if you use mawile (plus it’s really perfect for the playstyle - idk why you’d want to). Uxie is the most expendable of the four as I see it. You could justify using another attacker or bulky setter over a suicide lead if you feel the meta favors it, but really Uxie is it if you want to go the suicide lead route.
That leaves you with two slots that can change. Cress usually occupies the fifth slot (which really SHOULD be some kind of bulky setter), and for good reason - it’s hard to pass up on a bulky setter that combines a ground immunity (which the near-mandatory core of Alowak, magearna, and mawile is obviously really weak to) with a way to restore the hp of your sweepers. That said, I’ve used other bulky setters such as porygon-2 to decent success.
So really, there’s only one slot that’s totally customizable. The famous TR team someone built awhile back had crawdaunt here, which is a fine choice, but really you could be justified in substituting a lot of things here as long as it has some kind of speed control for when TR isn’t up (usually a strong priority move).
That’s my two cents on full trick room teams. The good news is that, despite the lack of customizability, it can still win on high ladder if played well. What I think could really make waves right now are semi trick room teams, on which only magearna would be mandatory. I think the meta is really unprepared for a core of two or three mons who thrive under TR, if only because no one expects it. But that’s all theorymonning - I digress.
E: oops I wrote an essay sorry