You cannot install any IDE, EIDE or ATAPI drive in a 6100 without a hard-to-find adapter that is occasionally stocked by an Australian distributor. You should be able to install any SCSI CD drive in the internal CD-ROM bay, but there are some potential issues with power supplies and heat dissipation, especially with CD-R and CD-RW drives.
2x is fine for playing audio CDs and for installing the occasional piece of software, but for playing multimedia applications and games, 2x is a bit slow.
This page describes the options for upgrading the CD-ROM capabilities on the Power Mac 6100 series. Power Mac 6100 CD-ROM Drive Upgrades PowerMac 6100 CD-ROM Upgrades Support this page!
