Lunchbox PC - Worth it?

[Isaac Asciimov]

Hello,

 

This is a puzzle I am struggling with and I would really appreciate your help. I am trying to build an ultra tiny, super portable yet fast PC for music composition and performance, coding, movies. Gaming is nice to have but willing to sacrifice or consider a eGPU perhaps. I would also like to test my craftsy skills and fit this in a lunchbox. I have found a lunchbox/case with dimensions 25cm x 18.5cm x 10cm or 9.84in x 7.24in x 3.93in.

 

So far I have found the following components that could be be fitted (perhaps):

M/B: B450 ITX

CPU: AMD Ryzen 5 3400G with Radeon RX Vega 11 Graphics

RAM: Patriot Viper Steel DDR4-3200 (2x 16GB)

1 M.2 and 1 SSD

 

And the question is regarding the PSU. Can I have a decent external PSU to power this setup, or do I need an internal one? And how much W is needed for this setup?

 

Thanks!