Looking for some BBT advice :)

Around what DPO should I expect an implantation dip (If it happens/if I get one)? Around what DPO should I expect a drop if AF is coming?

Should I only be concerned if a temp drop is close to the cover line? Are small drops normal? What DPO should I expect to test if my temps are still high?

I’m 4DPO, Thank you :)