1. The FPGA in the version 2 is different and it will not run the LimeDVB firmware. However it works OK if you select output to Lime mini.
2. The RF output on my example is about 30dB down on the version 1 on identical settings. I have sent a query to Lime Microsystems, but I wonder if anyone else has noticed this?
The RF output on my LimeSDR Mini V2 is almost exactly the same level as the V1.
Have you run a recent (since 30 Nov 23) update on your Portsdown? The LimeSDR Mini V2 needs updated drivers which are installed by the update process.