Yup, wider delts = lateral raises with STRICT FORM is a must and no swinging. If you are swinging your body and can't hold the lateral raise at the top for 1 count for all reps, throw your ego outside of the gym and lower the weight enough for 12 delt pumping reps x 4 sets. A tip is not to completely drop your arms at the end of a rep, stop at 15 deg from your body to let the muscle keep contracting.
If you want your arms to grow, just like any other body parts, put arms training for 1 day for arms only, and blast your arms kao kao on that arm day. It's not a good idea to train arms by combining arms with back/chest only, by the time you finish back, your biceps lembik liao and won't train as hard as you would on arm day, training your biceps first then back would cripple your back training, so you will end up not training your back and biceps properly.
Biceps is a small muscle compared to leg and back muscles. So a lighter weight is sufficient to stimulate it. Just make sure your form is perfect, ie no cheating and elbows locked to the sides of your body, you might want to cheat on your final reps.
A tip to make your arms LOOK bigger, is to train your triceps properly.
For arms, you need at least 9 sets of exercises (biceps and triceps EACH at least 9 sets, do 3 sets for each of the 3 exercises) involving different angles.
Speaking from experience.

that's true but that would not be possible if you're doing 3 day split...maybe combining body parts might not work for you but work wonders for many bbers...with correct forms and poundages, combining arms with other body parts (or combining any body parts) is just what you need for (as long as the format/routines you are using advocates progressive overload, mainly by encouraging progressively heavier weights to be used, and does not promote overtraining, should be no problem) ....