Should I create a Bootcamp partition (even if i plan on using parallels)?
I don't thinks so. I've been using VMWare (same way of working as Parallels) for years now without a partition and I've never suffered any issues.  

When using virtualisation software without a partition, the software creates a dynamic partition which will grow depending on your needs. So basically, it's the same. Only the dynamic partition is a virtual one.

So, in my opinion, there is no need to waste a predefined partition on your Macintosh HD. Just let the software do it's job and go with the dynamic partition.