I've spent years not targeting arms, just assuming the get hit in compounds. It seems to be fine for my tris but then I do like to press, never done much close grip though. But my biceps are a bit lacking, not like hugely disproportionate but obvious weakness if I were to be judged on physique. I've started doing some isolation but don't really programme them, just 3-5 sets of 8-12 reps but they have to feel heavy. I don't really worry about weight because what I've done before tends to have a significant impact on how much I can curl