I'm not an expert on the topic as while I have done this before, I'm not the greatest battler. But I know a thing or two.
First of all, those are some good choices for setters. Another one I see a lot is Bronzong, since you did let me know you were going that low to use Porygon2. Hatterene is also a popular choice. I'd recommend at least two setters, but not more than three.
Other than that, the sky's the limit as to what you can put in a Trick Room team. It enables you to put stuff in that normally would get obliterated in any other tier. In the olden days I'd put a Gigalith in for memes and Choice Band it and call it my sledgehammer. All you have to do is make sure your choice actually does enough damage to the threats you're anticipating.
But, even so, let's look at OU for starters. Perhaps you could put in Scizor, who's fairly slow at base 65 speed. If Trick Room wears out you have a backup option in Bullet Punch, or, God forbid something slower shows up. Alolan Marowak and Tangrowth have excellent offensive stats and pretty poor speed, although Tangrowth doesn't have the greatest movepool either so only use that for memes.
Finally, don't have everything in your team be slow. By no means does this mean make them go hyperspeed, but maybe have something to be able to set-up into it. For example, a long time ago I used Gyarados to Dragon Dance into the last turn of a Trick Room. You have to be careful when doing this, though.