Simple DMX controller

Hi, I have recently bought a strobe and I want to build a DMX controller for him, very simple with 2 potentiometers (to intensity and frequency) and few buttons for presets.

I just have some questions with the shield which convert ttl 5V to rs485: MAX485.

Is It well a 120 Ohms resistor include in the max485 or Should I put one?

For this simple electrical assembly wich only 1 slave, Have I to isoled the shield?

I'm a little confused to how isolated :

should I choose a pre-isolated shield like MAX13487, and wichever should I choose?
Or How to isoled simply the assembly, data and power? I know there are several subjects on the subject but I'm lost between octocoupleurs and resistors... ^^

Thanks for your help!

the 120 resistance between A and B