You are very abicious.
Braces are very difficult to use as dynamic clothes and you decided to start lerning clothing room with them ;)

Anyway it will works if straps are welded with cups and the rest of the mesh...

1. Load obj checking "weld identical verticles"
2. In clothing room select as a "soft decorated group" all non welded parts of mesh (I've seen tie between the breasts but there can be more of them etc.)
   3. Make "new dynamic group" and select cups. There is a chance that cups are already selected as a material ("add material"), if not you must do it manually. In "new dynamic group" set  fold resistance 50-150 and increase cloth density.
   4 In "default" group increase only density, do not change "fold resistance". Check what is selected as a default group - part between the breasts cup must be selected as default. Generally vetes sellecteded as a "default" group should be: arm straps, part of bra under and between cups, part on the back.
3. In posing room add "hi res square" on the floor and set your bra "laying back". Cups up straps down. Add sqare prop to collision list.
4. Calculate trial animation about 30 frames. Find frame where straps starting collision against square prop. Let call it frame "X". Find either frame when cloth stops falling down - frame "Y".
5. In frame "X" add keyframe to square. In frame "Y + 5" set  zscale to 150-200%. It should finally stretch arms straps more naturally - cups should be in the middle not hidding them.

Is it clear or should I add pictures? I haven't Hongyu's DreamLace but can try with another similar top.