Well, the parts already in there are a knockoff of the parts I'd recommend, so they aren't that different.
I wouldn't spend the money unless you want different color buttons.
Happ Super joysticks. For the buttons, some sellers like groovygamegear and focusattack offer different switch options if you must upgrade or want different colors.
The x-arcade buttons are only a quarter inch shorter. I don't think it will make a difference.
I'd stay away from convex buttons. I have them and on games that use more than 3 buttons, I find myself looking down at my hands more often to get them back in position.