i have black gold, keylime, caramel blend & peach all in concentrates to mix my own.
they all are strong enough at 5% 50/50 in an rda.
the only one i add anything else to is the peach which i add a drop or 2 of flavourarts >MTS to 30ml and it tastes awsome after a short couple of day steep.
black gold defo changes as it steeps, it has done when i bought it ready made and even had to add vg as it got to strong come the end.
i use 5% with most other brands aswell so its defo strong enough in the concentrate, but i can only vouch for the four flavours ive mentioned above.
flavourarts MTS you can get at liberty-flights and lasts ages.