Example: If I use your IP country selector to "force" the user to the correct store, how does that work with direct links (to product pages, blog posts, static pages)? For example, if I post a link to a blog post on Facebook and that link is to my International site (for all countries except Brazil) but the user is in Brazil, with they get redirected to the specific page, or simply to the homepage of the Brazil site?
The short answer is, this could be technically done, but it doesn't work like that out of the box.
The way that it's built, is to detect their IP, then point to the homepage if they're in the wrong country. I.e. if you have a US store and a Brazilian store, and a Brazilian resident visits your US store, they'll get redirected to the Brazil homepage.
With some tweaking of 2-3 hours development time ($120/hr) it could be set up to go to relative links, assuming they'd all been set up correctly on your side. For example:
If the person lands on yourusastore.com/products/some-product
Send them to yourbrazilstore.com/products/some-product
That could be done with some customisation, but out of the box it will point them to the homepage. If you'd like this customisation, you can contact us at shopifyninjas.com/contact.