I would say that it depends on what you intend to do with your small batch flavour trials.
If you want to take a quick taste, in a dripper for example, and throw the rest away then nic is not necessary.
If you want to vape your trials then you need the nic. If your nic level is low it won't affect the flavour too much, if you're at 12mg or above then it might.
When I started out learning about individual flavours I would make a lot of 5ml and 10ml testers, electronic scales are essential to dose them accurately. I did literally hundreds of test mixes in my first 6 months of learning DIY. To speed up the mixing process I made up a botlle of nic base using VG, PG and PG based nic, so that I was adding only 2 ingredients each time - the flavouring and the nic base. When I got a new concentrate in, a test mix would then take seconds.
Are you concerned about cost or accuracy? I don't know how much you've paid for your nic, but it's usually a small ratio of the cost of a juice in comparison to flavourings. My attitude towards this was that I was spending a fair amount of effort learning these flavours and how they mixed together. I would have been annoyed to get to the end of a trial and then find it didn't work when I added the nic in - so I did all my trials with nic, to avoid that nagging doubt. That was me ... and in truth I threw a lot of juice away in the early days, on reflection I'm sure that I could've saved a little money by trialling without nic.
I don't know if that's useful for you ... there are pros and cons, no right and wrong answer ... it's entirely up to you.