Once PC running with several different browsers would be enough with each using a freebie VPN if necessary. 9+ individual devices such as laptops or PCs would be difficult to house and maintain though not impossible for somebody determined.

It seems like he hid himself very well and posted in a way to not expose himself but thankfully in the end he got caught out but made a lot of money out of the Chipmixer signature campaign by cheating them and maybe from several other current campaigns with more connected accounts that have not been exposed yet.