Any conflicts expected with Joomshaper

Hello Nadja,
PageBuilder and Helix3 are based on "Bootstrap v3" CSS.
Cobalt's default template and markup is based on Joomla core "Bootstrap v2"!
So there might be some styling issues and visual glitches. Currenty I can't say it for sure.
The best advice is to simply test it. Both products have FREE versions. I would recommend to download and install them. For a Cobalt quickstart, you could use the free additional "Packs" in the download area ;)

It might also depend on your type of usage:
- Where and how do you want to display PageBuilder content?
- Where and how do you want Cobalt to appear?
- Which base/main template are you using?

IMHO, you won't really mix both products, except for the ususal Modules.
I assume you have sidebars with modules, or show Cobalt modules inside PageBuilder pages?!
I would not recommend to use the PageBuilder INSIDE Cobalt.