3 Phase 3 wire delta, current transformers and lots of questions
Will 3 wire Delta pass through a single CT and function as normal,
  reduced or just not possible at all.


No that won't work under any normal load conditions because the instantaneous sum of all three currents is zero for a perfectly balanced load. 


  Will I need to have 3 CTs wired in series with a relay as load w/ or
  w/o a resistor?


Just one CT attached on one phase is sufficient because if one phase is taking current then the other two can be presumed to be taking current also.

Will it drive a relay? I don't think it will because the relay coil doesn't represent much of a burden resistor and the toroid core may sature and you'll not get enough to power the relay. However, that is a generalization and you might find one that works BUT you are now starting to have problems deciding which cores will saturate and which won't.

Almost certainly, a more reliable solution is to use a conventional CT with a burden and use the signal to turn on a transistor that then activates the relay.