It's complex to assume anything about the power levels yet because we have not seen all the Harbingers in the game yet. Also, the Traveler's powers are still in a cloud of judgment on what kind of powers they can rely on or morph into something else. We saw Traveler's powers in a fight against Childe, where they used double elements to resist an attack. Still, no comparison can be made with him. Childe was using an Electro delusion to supplement his powers. It was fascinating to see the Traveler using double elements. There are a lot of interesting theories about this made by the community on Reddit, and I advise you to take a look at them. Some awesome lore enthusiasts in the community pay precise attention to the details and draw valid conclusions. I'm sure you must be able to find some interesting reads about the Traveler's powers and how their experience is going with the elemental powers. One thing is sure that they rely more on swordsmanship than the elemental powers and slowly learn to use them and refining as we go through other regions. We can only hope that we get to know more lore in the game and see how the events will unfold in the future.