Slackware is not an rpm based distribution so I recommend not using rpm's, the dependancies won't work.
If you want to install kylix just download it, and the upgrade, and install them. It should work just fine. Don't go replacing your glibc with an older version, you won't like the results
As far the directory structure goes, Slackware was basically the 2nd linux distribution ever, after SLS. It has pretty much kept the same directory structure since the begining of time. It is "linux as linux was originally intended" if you will.