Hello @dxxx0001 and welcome to the ST Community.
You can config a BLE P2P Router that does include both server and client on the same device. For the wireless stack, both full and Extended can do the job but the full can do the job with less impact on the memory. You are using the STM32WB15CC, so you have to test it if the code will fit on the memory available on the MCU. The BLE_p2pRouteur was implemented already on the STM32WB55 (link attached) with 1M flash. For the difference between both wireless stacks, the extended stack have the same features of the full stack and it implement also the following features :
- L2CAP connection-oriented channels support (IP over BLE enabler)
- Channel selection #2 (under application flag selection)
- BLE Extended advertising (under application SHCI_C2_BLE_INIT_OPTIONS_EXT_ADV flag selection with following limitations on currently supported configurations as (max sets number, max advertising data length) equal to [(1,1650),(2,828),(3,414)] such as both parameters are compliant with allocated Total memory computed with BLE_EXT_ADV_BUFFER_SIZE based on Max Extended advertising configuration.
- BLE GATT caching supported (certified BLE 5.3)
- BLE Enhanced ATT supported (certified BLE 5.3)
More details are available in this Wiki where you can find the table that associate a stack to each application:



Best Regards.
STTwo-32