I still would like to know if the two wires coming from all 20 light bulbs, ground and power, need to be connected to the same terminals of the transformer. In other words, what if 10 bulbs wires went to different terminals then the other 10 bulbs? Is that a problem? I attached a crude diagram to illiterate my question.
There is only one transformer in the case. Splitting the load between two different terminal post will not change the load on the transformer. You should use use the terminal posts that give you the voltage you need. As Rob said, on the 1033 the A post is the common post. It would be best to use it that way. Also the transformer should be in phase with the other transformers you are using so inadvertent contact does not result in an unnecessarily high voltage fault.