Bronze in C&W is an age division--I think it's 40+ in ACDA, (30+ is Copper) which is who runs the event in Houston you are going to, SPratt. I think they do still require a yoke, and a "country" look to the costume, though UCWDC doesn't--but UC is more restrictive on the stoning at the newcomer level (I think.) You should be able to get plenty of information at the studio about costumes, etc. Your instructor is very experienced and there are several C&W competitors there.
I asked Dave Getty (the one who writes the rules) about the UCWDC's stance on "the yoke." He said "no," that requirement has been dropped . . . BUT . . . there has to be a distinguishable difference between the top and bottom of the shirt/blouse similar to a yoke . . . for example . . . color, material, stones/glitter and the likes, patterns in the material . . . but the definitive "cowboy yoke" is gone. The separation doesn't even have to go straight across, etc. Backless and and bare midfiff is now allowable.