Cremeux is nice, honeycomb latte too - although the latter was a Christmas limited edition, not sure if it's being continued or not.
Imo both better than blood of Vikings, which has a bit of a tang from the rhubarb on the aftertaste. Brain twister is pretty good too, but for me it needs to be run hotter than the others.
As for risking concentrates - 250ml starter kit gets you concentrate, 250ml of VG and a handful of nic shots for £11.50 (current special offer). That Vs £9.99 plus a nic shot on a shortfill - no contest
You get too much VG in the kit too for the recommended mix ratio, so 40-90ml (depending on flavour and nic strength) leftover for other mixes.
Obviously - personal opinion, taste is subjective etc.