Cream mixes are tough. The good ones all contain diacetyl. Bavarian seems to be the cream of choice for a lot of DIYers. I think a neutral cream flavor is best without sweetener or vanilla. I use whipped cream and leave it at that.
I recently did a drip taste test run-off in my IGO-L, and found VZ's SC Cream to be my favorite. Here are my notes on creams and some related flavors -
VZ Cream 8.5 Y this is as good as any of my “creams” Nice and rich
RTS Catalan Cream 7 M A bit sweeter and with more vanilla
RTS Vienna Cream 8 Y very similar to above, but a bit better
VZ Caramel Candy 7 M Mild and sweet
Dekang Cream 3 N Not as pure tasting. Use it and lose it.
Dekang Caramel 4 N Same, with a touch of coconut
VZ Caramel 8 Y More like toasty toffee. Nice, but certainly a burnt sugar taste in there.
Dekang Butterscotch 5 N Best of the DK's here. Tastes like a butterscotch drop hard candy and blends well with the VZ Caramel
RTS Custard 4.5 N Not as strong as I gathered from previous use. Doesn't over power the remaining butterscotch still in the drip wick like I expected. A bit of an off/plasticy taste, but not horrible. No need to re-stock it though
RTS Almond 7 M/N Much like a coffee almond flavor additive. It's ok
RTS Nut Mix 7.5 M Ok, a toastier mix, but not obviously “nutty”, so much. I still like it better than the almond. Quite mild at current concentration (5%)
VZ Vanilla 6.5 N Vanilla with a touch of cinnamon. Ok, but not a true vanilla taste.
GeJ French Vanilla 8 N Rich Vanilla. This is way better than the VZ
RTS Bourbon Vanilla 8 Y Just like the GeJ. Nice! So I have one that's right. This is a good mixer, and what I like in a vanilla flavor. Sort of what I wanted from “custard”, but that one is not so good.
#'s are my rating 1-10, Y/N/M is would I buy it again