About screen layout on iPhone: I assume you are talking about the landscape layout because in portrait layout there is no arrow visible. If you your focus is lyrics, then use portrait layout. It will maximize the visibly lyrics area. Landscape layout does not work well especially on iPhones X and later because of their screen ratio.
I'm not going to change the sizing and placing of buttons. They have exactly the right size to hit them. I would definitely don't want to have them smaller.