I never heard about different banns from Nintendo. If a Switch is banned, the Switch is not longer able to access the Nintendo servers. It is only a serverside refusal and nothing hardware related.
So a banned Switch should be working propperly and only have no access to the Nintendo online ressources
There was a time (apparently) where there was user level bans (account style bans) in which the user account was prohibited, not sure they do this anymore and it’s all “system” level bans
As for the OP question, [online nintendo server functionality] this would be tied to the SoC and EMMC, everything else (hardware wise) is usable for transferring to another board
Though, it’s worth noting, if your had a board which was unpatched but banned, they still have value given how rare unpatched boards are becoming and you really ought not use it as a donor even if it’s banned