Burning Bootloader to Custom Board(s)

I am designing custom PCB board that will go into rc plane and save GPS positions onto a micro SD card.

So I looked around for different Atmega controllers, and ATTiny 84 seems to be best matching one I had in mind for current target design and future expansion.

I also aim to have two different versions; one with USB connector so it can be programmed via USB port, other with FTDI Breakout.

Question is, what tool(s) do I need to burn bootloader to my custom board once I finish making it?

I saw Pocket AVR Programmer sold in here https://www.sparkfun.com/products/9215, but will this also burn bootloader to custom boards?

Last but not least, do I need to manually add custom board type/definition/hardware for ATTiny 84? I’ve seen couple of ATTiny 85 board but haven’t seen ATTiny 84.