How to test new ad creatives within a relatively successful campaign

Hi, I've been running a campaign that has been relatively successful for us so far for about 7 days. I have been thinking about adding / testing 1-2 more creatives and wanted to seek out best advice on how to do it.

Campaign Structure:

  • Purchase/Conversion objective
  • 2 Ad Sets:
    • Ad Set 1 doing interest targeting 
    • Ad Set 2 doing broad targeting 
  • 4 creatives within each ad set (same 4 within each ad set)
  • Spend: $75/day (just increased it)

Performance (over last 7 days:

  • Purchases: 16
  • Frequency: 1.8
  • CTR: 2.8%
  • ROAS: 1.8

Questions:

  • I have created 2 more creatives that I'd like to test - should I do this in a wholly different campaign, or just duplicate the current 2 ad sets and test the new creatives there?
  • Is there risk to just "adding" or swapping out one of the creatives in the current ad sets to the new ones?
  • Is it too early to be testing new creatives?
  • Is 2 ad sets, with 6 creatives each, too much, considering my daily budget of $75?

Appreciate all insights and everyone here!