If I have a hydrocele, does it help to wear boxers instead of briefs?

Yes and no. What you wear does not affect the hydrocele. However, if you have symptoms, briefs may provide more relief.
Depends on symptoms. Briefs for men are like bras for women. Briefs support the dependent structures (i.e. The scrotum) if the scrotum is larger from a hydrocele (fluid collection around the testicle), when standing it may pull on the testicle and stretch the cord structures associated with the testicle- supporting the weight with briefs may be more comfortable. If symptoms seek surgery/urology advice.