I use a 1 L. aluminum pot & lid and a PLASTIC drinking cup W/ graduated markings (for measuring)

WHY would I carry a Ti cup, single OR double walled??

Yes, a single wall large Ti cup can be use for "cooking" (i.e. boiling water but not true cooking) but not so for a double walled cup. Very inefficient.

To me the Ti cup thing is the current version of the stainless steel "Sierra Cup" of the '60s. Neither makes much practical sense. But, hey, they look cool.