I'm an 18mg kinda guy most of the time, but recently got a load of 24mg juices as at the time it was all the vendor offered, save for one, I actually didn't really notice much difference. I think it depends on the type of juice. On sweet, fruit or dessert flavours, they say more nic will give more of a peppery taste and throat hit to them. On tobacco flavours I think it adds to the 'raw deepness' of tobacco, can help pronounce the earthy flavours and really help with throat hit. I found this especially true on a Dekang based Ry4 recently where, until steeped for 1.5 weeks it was excessively harsh.
Delivery method will help too. Try a dual coil cartomizer. They give out hot vapour and Throat hit is definitely stronger on them then say a standard boge carto or a CE2 for example. I wouldn't worry about vaping 24mg straight too much, it's not 'that bigger' jump up from 18mg really. If you were talking 36mg or (heaven forbid above) then sure, I think you'd have more to worry about.