The flavour from different makers varies, sometimes dramatically.
Not just the % but the actual taste. One makers Strawberry at 15% can be COMPLETELY different to anothers at 15%.
Not used Flavour West really so cannot comment, Bluberry does tend to be a fairly strong concentrate from my memory (not used in ages).
Also, just for another twist and head screw........flavour is subjective. One man will say I mixed at 7.5% and the flavour was insane, someone else may need 18% to get 'hint' of that taste.
Then we throw in VG%, steep time, tank, coil ohm, wattage, DTL, MTL, Muji, Cotton Bacon, Mesh, Temp Control, nic strength........
Not 'easy' to find what suits YOU but when you do as long as you have records it can be re-created
.