Moving a Teensy-based custom PCB to use an ATmega 32u4?

[ngaalex]

I've designed a custom Teensy-based PCB for a 9-key (3x3) chording keyboard prototype, and in an effort to reduce size and learn more I've moved the ATmega 32u4 from the Teensy to the PCB, along with (I hope) everything else needed to get it to operate as a keyboard - working from Teensy and Arudino designs that use the 32u4.

In terms of bootloaders, is there generally a default for the 32u4 or will I need to flash one via ISP?
And if there's anyone experienced reading this, how would you assemble it (solder it yourself vs. spend the extra money to get it assembled) and would you be able to check my KiCad PCB/schematic design to verify that it's all there?

My plan is to use this keyboard as a learning experience and eventually fully design a PCB that's usable for everyday use, so I'm definitely open to any pointers or anything that'll help me towards that.