Catch can is up to you, some people fit some don't. If you get rid of the soot via the egr block then it can't mix with the oil in intake which the catch can would remove so can't form a sooty deposit. I think you will find most people with crd just do egr block.
Scanguage 2 is great bit of gear, you can use it to check your boost isn't spiking once egr blocked, shouldn't be issue as crd motors seem to be pretty good at controlling boost. Can also help you learn to drive more economically, and can monitor few other things like coolant temp.
I think you will find the crd is pretty reliable compared to the early DI. There is some around now with some pretty high km on em.