I actually think it's great, that someone, like the OP, isn't copycatting others designs, but rather utilizing what he sees and tries to improve his/her skills.
One of the things which is hard to comprehend is..... someone learns by making mistakes.... your own mistakes. If all one did was to take all the good stuff, copy it, they haven't learned a thing. Whether you're honing your skills to be a designer or doing a math test, you won't learn a thing by copying. Take what you like from here or there and make it your own. Once you know the reasoning or math theorem behind it, it will make all the sense in the world.
The difference in letter heights is not a 'right' or 'wrong' process, but a personal preference kinda thing. To some, it becomes aesthetics, while to others, it becomes an eye sore. My question is..... why is the
J so much larger ?? Because it is more important ?? Is it his first name ?? What function does it serve being so much larger ?? He answered it. He just likes it. For me, it becomes a focal point and other than he likes it, it makes no sense. His reason is weak, but it's an honest reason.