I have come to the party late so I am a little confused about RPM. Is RPM to be a replacement for Warpin or are they be be used together?
RPM is the redhat package manager, quite different from WarpIN which is an OS/2-aware installer. The promoted builds of RPM are only a subset and definitely not OS/2 Warp compatible. It's some kind of experimental stuff nothing for production use. If you wanna play with RPM you can still find version 3.0.6 which is an OS/2 application that can recognise at least OS/2 file names.
The package format is different but both use bz2 for compression, newer RPM also use xz for their cpio archives. So you really don't need rpm to grab the content of a RPM file. cpio and bz2 or xz and some shell script should avoid the bloatware approach in most cases.
Is Warpin to be used for ArcaOS developed programs and RPM to be used Linux ported programs?
There were no ported programs for the average user from Linux in the last years to mention. I only remember some ethernet and AHCI drivers.