Building such dev board shields/carrier boards is a nice beginner friendly way to get into electronics and pcb design.
What are some of the typical tool people use? I used EasyEDA because the board I was modifying was already in their system and their coupon made ordering the PCBs basically free (I think I'm paying $3 for 5 PCBs + shipping). However that software felt a bit unpolished, are there better alternatives? (granted, most of the EE software I've used feels rough, looking at you Xilinx)
All of the low and high code board houses will support either kicads project formats directly, or kicad supports standard Gerber format export.