What do multiple slashes in METAR mean?
Complete, unless you want to know the height of base of those TCU's!

The bulk of the information you're after can be found in AIS-GEN 3.5 Section 10.17 - AUTO METAR coding

In describing the coding used by automated systems, it gives this example


  NNNhhh/// Cloud detected, but it is unknown whether it is a convective cloud type (ie TCU or CB)


And this one


  //////TCU Towering Cumulus detected, but no information on its height or cloud cover is available


Which more-or-less covers your two questions, I hope.