how is lead any harder/different than top rop climbing?
what about the belay technique?

Taking the rating of the route out of the equation, l have to say lead climbing is harder because you are toting more hardware up the route and you are usually climbing more than one pitch, so you need a bit more stamina to complete a lead climb.

Belaying is not any harder. l do not think it is all that different either. It just takes some getting used to managing the ropes while you are hundreds of feet in the air.

If u fall off on top rope u might fall 2-4 ft depending on rope stretch & get a mild scrape or bruise. If u fall while leading u can kill yourself, & possibly ur second if u have not built a decent belay. This will become apparent to u when ur 15 feet beyond a dodgy RP placement.

From u question u do not know enough about climbing to be safe. Take a decent class at a local wall or climbing gym, then u can enjoy a great sport throughout a long life.

Your head (fear) is not in the way when your on a top rope. The simplest difference in belay techniques is that when top roping your mostly taking rope in, when your belaying a leader you are letting rope out (cautiously when the leader is clipping) and taking it back after a clip has been made, and you need to be ready at any moment to catch a leader should he or she fall.