I never use the Instrument Assistant, so I am not sure what it does. I just use the VISA Write and Read VIs.
Usually you can just use the default LF as the termination character. The only time that would be a problem is if the instrument is sending binary data and a LF character can occur in the data set. The other thing you need to check is whether the Instrumentation Assistant sends termination characters. By default the VISA Write does not do so. Even if IA does append a termination character, it will only append one character, the LF. So you still need to explicitly append the CR, and probably both CR and LF.
For receiving you definitely want to use termination characters because you always get complete messages so that the parsing is simpler.
Lynn