Unless you are going crazy high in nicotine I doubt it will affect your mix, and if it does, it's kind of a peppery/harsh taste. I am going to agree that Bavarian crème needs a steep, and honestly, I'd expect a hint of strawberry taste, but I don't know-- I loathe fake strawberry flavor, so I don't use it. But berries generally only require a rapid steep-- in fact the first time I mixed Forest Berry mix (FA) I had to cut it with a LOT of brandy (sour tasting brandy) and a hint of chocolate to even get it vapable it was so sweet and overpowering. Maybe give that one a few days, and then depending on what's happening, you might need to add more/add some sweetener (just the tiniest bit!) or even another flavor like cotton candy or marshmallow (both naturally sweet) to give it some background flavor.
BTW-- this is EXACTLY how I started mixing. Single flavors that I'd steep for a while, then amend as needed and it's a great way to learn flavoring profiles. I mixed up 15 3 flavor, with SOME sweetener in some, and they all turned out almost exactly as I had planned, which was fantastic. Once you learn what your palate likes with what, you will be much more confident. I prefer that to cloning a recipe but that certainly does have it's place. Let them hang out for a bit, vape and see what you taste, and what you need to add.
I suppose it is possible that nicotine could mute some flavors, but I don't see it as super likely, and though 18 nic seems high, it's really not high enough that it should be affecting flavor much unless it's older nic.
Best of luck
Anna