In which timeframe did you use CFW? In the beginning there where bugs that caused some logs to be created, but Atmosphere added many protection for log creation and sending.This depends, if they do the same with they did with the NES emulation, then yes its possible, I do not go online and i do not have a subscription. But i play the NES games.
There is compiled NSP complete with Games AND OR additional games not on the current service.
Also in relation to banning, its not just pirated games, I bought my switch, used CFW only for emulation.
It was this that got me banned (I suppose Emulation is a form of Pirate, but Retro Arch crashed, must of sent a log to the server and about a week later i was unable to access the online services)
So did you realy not do anything else? Like install a homebrew nsp, cleared logs, cheated, used romhacking accidentally online, used SXOS without creport and whent online with ofw afterwards, experimented with things like the dev menu, or something similar small but flagging?
I'm using CFW on both my switches for years now, and even multiple family and friends switches are 100% of the time in CFW, none of them is banned yet.