Beyond the reasons you listed, it’s also been helpful as a tool for gear research. There are other tools for finding images taken with a certain lens or body but it is a useful alternative.

I haven’t gotten into canvas prints but use Costco, which recently partnered stih Shutterfly. Their regular prints do not have watermarks but their books have branding, I believe. Wish I had a more helpful answer!

I will let others comment on what online printers are available for Portugal, as I am unsure. However if it’s anything like what’s available in the US, oftentimes there are different storefronts like Walmart or Target, but they end up using the same exact printing facility. So it’s the same quality but with different watermarks and prices.
I hope you find a solution. Printing your images out is as magical.