@Andrew Allen good question, and it's the right thing to dig into before locking in your telemetry architecture.
The 50km figure is the drone-to-drone spec achieved with the external amplifier stage and optimized RF design — that's already pushing the hardware pretty hard in ideal line-of-sight conditions. The 2Mbps is the raw PHY data rate, not the mode that gets you max range. If you drop to coded PHY at 125Kbps you're getting roughly 3dB of coding gain over 500Kbps and about 6dB over 1Mbps, which in practice translates to meaningful link budget improvement. So yes, there is a tradeoff happening and no, those two numbers aren't from the same operating mode.
The honest answer though is that for a remote telemetry project you probably don't need 2Mbps anyway — telemetry data is almost always low-bandwidth, so running coded PHY and squeezing extra link margin out of the radio makes a lot more sense than keeping the high data rate. Whether you'd push meaningfully past 50km in drone-to-drone config at 125Kbps depends on your specific environment and antenna orientation, but the physics say you should see improvement. Worth running a field test and logging RSSI at both PHY settings to see what your actual fade margin looks like at distance.
