I think you'll be pretty happy using MiniCore with ATmega328PB. There were initially some issues with Arduino's beta version of the AVR toolchain that adds support for the PB chips but things seem to have settled down now. It does add a couple extra steps to the MiniCore installation process but that's just installing another hardware package via Boards Manager so it's easy enough.
Of course I'm also a big fan of ATmega1284P and family but if you only need the two extra pins that might not be the best choice for your application.