Does your plan information list an expense ratio? Typically that information is make public to the participant.

It seems a little odd that they would use the S class. Is this a small company?

I've seen *.lw share classes (typically A shares) where the .lw means "load waived." That also often means no 12b1 fees but I don't honestly know if Janus even has a 12b1 fee. It is possible that they are using the S share class to provide compensation for the company managing the 401k - even if that company is Janus.

You should be able to request a prospectus that would detail exactly what Choice Class 1 means.

As an alternative, you could also try calling Janus directly. I've done that before to get answers about their funds.