[CHAT] Question about the level of detail in pattern making programs

I've only recently rediscovered cross stitch after many, many years and am really enjoying it! I've almost finished my first item, a little kit cowboy, and am looking to my next project.

I would like to do a cross stitch of the Disneyland castle, but not a lifelike image, more a 2D colour-blocked drawing of it (almost Mary Blair style but more pastel, for those who know Disney). I've found the image I want to use (and have requested permission from the artist) and had a look at some free online pattern generators, but I'm not sure how to gauge the size/amount of colours to use. The images of what it would look like are kind of blurry around the edges instead of nice, sharp lines because they use too many colours, but when I reduce the colours, there doesn't seem to be enough.

Can anyone please provide some guidance on pattern generators and how to use them to best advantage?