Is Twining needed to solve environmental puzzles?

In practice this means the human character is not a complete kit on his own. He walks, he fights, and then he hits something he cannot get past. The way through is to merge into one of your Aniimo and use that creature's abilities instead of your own. Outside of combat, that is not a shortcut. It is the intended method for environmental puzzles and for crossing terrain.

So when the open world stops you, the first thing to check is your team rather than the geometry. A wall you cannot climb or a gap you cannot cross is usually a form problem. The same Twining you use to swap forms mid-fight is what opens the map, which means the Aniimo you carry for combat also decide which parts of the world you can reach.

The puzzles you will actually meet

The overworld puzzles are physics-based. One recurring type asks you to replace a missing center piece, so the solution is an object moved into position rather than a switch pressed.

Field abilities are the other half. Water abilities, for example, are what let you interact with environmental water puzzles at all. Those same abilities are required to reach specific overworld areas, so a locked-off stretch of map can come down to whether you have the right ability with you rather than whether you have solved anything yet.

Not settled: Whether any of these obstacles have a second route that the human character can take alone is not settled.