I think only India has a different naming scheme. So,
India's Redmi Note 5 Pro = China's Redmi Note 5 =
Singapore's Redmi Note 5
India's Redmi Note 5 = China's Redmi 5 Plus =
Singapore's Redmi 5 Plus
At least that's what I concluded when I was deciding which phone to buy. I didn't end up with a Note 5, so perhaps someone can verify the above.
When buying from third party resellers, the easiest way would be to check the processor. One is Snapdragon 636, the other Snapdragon 625. Cannot go wrong one.
Rather than check if it's "global rom" or not, I believe it might be wiser to check if it's a China set or not. Sellers can and will flash global rom over China sets, then tell you it's a global set, but China sets might lack certain LTE bands. When I was researching, people mentioned in this thread that Redmi Note 5 (SD636 one) China set has no band 20. Extech explained more about this on the previous page.