Ollie you can connect a mixer to a laptop but for sure you will not get a good sound.
If you just want to connect a guitar plus a mic, then you don´t need the mixer as you can connect both to your UX1 which by the way is great and get a very good sound.
If you want to connect more things, then you will need the mixer which can be connected to the UX1 from the 1/4 main output and then to 1/4 input on the UX1.