You don't need a physical mixer unless it's a live situation. I mean, you can get one but it'll add very little to your workflow if all you do is make beats.
Depends on how you work it into your workflow.
If it's difficult and tedious to set up with your DAW and you have to spin your chair 180 degrees to access it,
you'd probably be much better off without it.
If, on the other hand,
it's well-integrated with your DAW and you have the device front-and-center where you can always see and reach it,
there's a great chance that it will be indispensable.
One of the reasons I went with REAPER as my main DAW is that it has fantastic support for the MCU Pro
written by an outstanding third-party developer who goes by the username Klinke.
The value in each of these control surfaces comes mostly from how well they're integrated with your software rather than in the cost of their moving parts.
Because of that, YMMV drastically depending on your DAW of choice.
Pro Tools, Cubase, and REAPER each have numerous control surfaces that work fantastically with them
(several are pictured above).
Live has its own specific control surfaces
(Launchpad, Push, etc.) that work really well for it.
Control surface support for FL Studio and Reason feels a little bit forced by comparison, as their flexibility ends up making it difficult to map controls in a consistent and useful manner.
-Ki
Salem Beats