In a nutshell, BIAS AMP 2 DESKTOP focuses on amps only, it has no effects. Here, you can design your own custom amps to really focus in on the sound that you want out of your amp.
BIAS FX 2 DESKTOP contains both amps and effects. You can import your BIAS AMP 2 amps into BIAS FX 2 if you wish. But BIAS AMP 2 is certainly not required to use BIAS FX 2, which contains many great amps already. (not to mentioned the thousands of amp options already in the BIAS FX 2 Tonecloud)
Please refer to below links for comparison charts:
BIAS FX 2 Comparison Chart
BIAS Amp 2 Comparison Chart
Technically, you need an audio interface(ADDA) for plugging guitar signal in. By doing so, you can play and record through the audio interface with Bias FX/Amp.