Cheers Stuart, really appreciate all the info and links. Think the last link is very useful but not clear it really answers my question--will certainly study it again later. I appreciate the brush tutorials if I ever need to do that they will be helpful. However, I already have what I need that I created in AI over the years--"true" vector brushes (see attached). I am trying to convert all of them to PNG for Designer and not quite clear on scalability relating to resolution. Why they are called "vector" brushes in Affinity when they really are not is perplexing but I digress. These will be for textures similar to that old "airbrush" look and stippling effects, so will not be a dominant aspect of the posters and doubt I will use over 600 pixels in size in any of my poster sizes (A0/A1). So if my final document output in print is ~150 LPI I could achieve a "crisp" look with PNG brushes created at 300 DPI at 600 PX in diameter? Even if I resize a vector object here and there within the poster during the creation? Is that what you are saying? Just attempting to figure out a "best practices" formula that illustrators like yourself use that I can apply to my particular situation.
I have experimented with this but have never printed something out at a print shop, just zooming in on a 4K display. Three things I would like to do. One: avoid, if possible, having to go to press as a trial and error process; Two: bloat my files with unnecessary resolution settings; Three: have the ability to scale elements upward during the creation process without loosing the resolution. Perhaps I am missing out on the overall concept of why Affinity uses the method of rasterized brushes in a vector application. In theory I love the idea but mixing resolution-dependent with resolution-independent seems counter intuitive when Affinity offers these personas in Designer and Photo.
Not trying to fight this just trying to ensure the fidelity of my printed artwork and wean myself off of AI. At least in Illustrator I knew the outcome was going to always be crisp no matter what size I printed. Surely Affinity realizes a need for this type of information when most of its customers are coming from a complete vector application like AI with "true" vector brushes.