Around 10mcg per spray is a reasonable starting concentration IMO. That way you can test over a decent dose range with a reasonable number of sprays.
Stick to standard 6% Neroli for scent. This settles lightest whilst maintaining a good even diffusion and is least problematic when used alongside other scents.
Going for any other scents/strengths will make your testing more difficult because you will have a more limited number of sprays before the scent gets overbearing - Also, some of the scents don’t diffuse as well and may clash with your primary/cover scent.
Once you have your dose range for a variety of situations/combinations, it is of course fine to use any dose and scent you like but bear in mind that some don’t diffuse as well and may clash with your primary/cover scent.