Reply to Serato Scratch Live Setup

Hello,
I ask some questions about the setup of my mixer Behringer DDM4000 and Serato SL2. I would like to understand if SL2 is ok or I need a more complex version (I believe I need SL4 but I am not sure). I do not know how Serato and the mixer work together.
I would like to know if it is possible link to my mixer:
> 2 turntables (I have Numark TTX1) + other 2 turntables (or 2 cdc or for example 2 hercules all in one controller)
> + 2 microphone (mixer supports them but it has not internal audio device)
> + 2 active speaker (mixer supports them but it has not an internal audio device)
> Serato SL2

Can this setup work correctly or should I use a Serato SL4 instead?

Another question. Are the two usb ports of my Macbook sufficient or not? What needs to be connected directly to my Mac?

Many thanks in advance and regards,
Stefano