Run a dedicated UGC campaign, separate from BAU, so results stay clean. One ad set per creator, each with its own budget: nothing gets buried, and you see exactly what each creator's content does in isolation before deciding where to scale.
Ad set 1: all UGC content with broad targeting
Ad sets 2 to n: one per creator, with creator audiences or broad targeting
Use ABO in the testing phase, so every ad set gets a fair test
Minimum daily budget per ad set: your CPA times 50, divided by 7