I'd go with the Pyroar, Heliolisk, Bibarel (for now at least), Diggersby and then maybe PorygonZ and a physical tank like Snorlax but idk.
Btw if this is about Reborn then it's better fit for the Team Showcase section.
Solving the Aventurine woods puzzle requires a lot of exiting and re entering using Tauros to hop ledges. If you can't figure it out go to a different entrance and try something different.
Of course my monotype experience was in Reborn and not competitive, but Steel was the most fun and challenging monotype for me. The balance of challenge wasn't too impossible but kept it fresh and I always had to plan ahead. The team is my TC if anyone's interested.