Aston Villa's Thierry Katsukunya doesn't currently have Wales as a nationality. He's been selected in Wales Under 19 squads (latest one here: https://www.faw.cymru/en/news/cymru-mu19-squad-announced-scotland-double-header/). I think it should be set as his first nationality, with the others secondary.
Liverpool's Lewis Koumas should probably be set as Wales first nationality, the others secondary, as his dad (Jason) played for Wales and Lewis has been called into the same squad as above.