The 6GK7342-5DF00-0XE0: Mounts on the S7-300 rail – same mechanical footprint as any standard S7-300 module. IP20 means it's for cabinet use, not field exposure. Communication speed on the PROFIBUS interface auto-negotiates from 9.6 kbit/s to 12 Mbit/s. Address range per DP slave: 244 bytes in and 244 bytes out; diagnostic data up to 240 bytes per slave. You can hang up to 4 of these CPs per CPU and a maximum of 28 DP slaves per CP when the CPU is on DP, or 32 slaves without DP on the CPU. That's enough for a medium-sized line section.
One note for the procurement file: this CP requires STEP 7 V5.1 SP2 or higher, or STEP 7 Professional V12 (TIA Portal) or higher for configuration. No special license needed beyond the standard STEP 7 package. The module is addressed via the rotary switch on the front – standard S7-300 practice.