Our admin docs list the latest version that we have tested and verified. It's possible, but not guaranteed, that it will work properly with newer versions. The fact that 1.14 seems to work for your user is encouraging and we may update the doc if and when we perform a full validation that 1.14 works correctly.
TensorFlow Model API deployment will not work for TensorFlow 2.0 because there is no C API support for TensorFlow 2.0 yet. However, plumber API support is available, and you can try using the tensorflow or keras R packages to load your saved model and issue prediction requests.
If I understand correctly, Tensorflow does seem to have c support now but the documentation for Connect indicates 1.15 is the latest version supported. Any updates planned?