I can't fully answer your question but I did once spend about a week porting plain internal configuration to cue, jsonnet, dhall and a few related tools (a few thousand lines).

I was initially most excited by cue but the novelty friction turned out to be too high. After presenting the various approaches the team agreed as well.

In the end we used jsonnet which turned out to be a safe choice. It's not been a source of bugs and no one complained so far that it's difficult to understand its behaviour.