I am affiliated with Instana :) So happy to answer your questions any time.
Instana automatically traces vert.x distributed and cross language - no configuration or code edit needed. More information on the Tracing approach, supported technologies and frameworks as well as customization possibilities (e.g. SDK) are available here:
https://instana.atlassian.net/wiki/display/DOCS/Tracing
We also support OpenTracing - in case you already implemented that.
If you have any questions: happy to answer them anytime.
Cheers,
Michael