Well after swapping the soc to another board I get the exact same issue, so I can say with certainty that the SoC is dead.
I definitely learnt my moneys worth out of this particular switch at least
Thank you @Severence and @SheriffBuck for the assistance on this one
(For those who stumble upon this topic with a similar issue)
With the official charger;
0.07a draw with no nand module
0.08a draw with the nand module
0.22a draw with 5v usb pc connection
Can accept and display payloads
Black screen when booting normally, no backlight
Black screen and no backlight when booting into original firmware from hekate
Freezes on the atmosphere logo when booting into custom firmware from hekate
Freezes on l4t logo when booting the linux for switch
SoC warms up as expected
SoC makes the chirping sound (confirmed on a working switch)