I am confused regarding countries being in multiple groups

So for example, I have central and eastern Europe including Russia, but also it's own category. Also Wales is its own category but also included in England and Northern Europe. I have ancestors that stated they are from Slovakia and Belgium, which category is the most likely to apply them to since multiple include them? Regarding the Russian, is it more likely my Polish ancestors were mismarked by the test or that they had some Russian that they didn't know about? (I did try searching for answers before asking so please have patience for my confusion) Regarding looks, I usually get told i look polish, occasionally that I look Irish or Welch so the percents are a bit surprising.

So for example, I have central and eastern Europe including Russia, but also it's own category. Also Wales is its own category but also included in England and Northern Europe. I have ancestors that stated they are from Slovakia and Belgium, which category is the most likely to apply them to since multiple include them? Regarding the Russian, is it more likely my Polish ancestors were mismarked by the test or that they had some Russian that they didn't know about? (I did try searching for answers before asking so please have patience for my confusion) Regarding looks, I usually get told i look polish, occasionally that I look Irish or Welch so the percents are a bit surprising.