Sure thing, so as a part of the SM, we are competing with other EU countries on trade. Some subsidies or support can be considered to give a competitive advantage, and if they don't, it's probably making our products less competitive to EU counterparts. The higher our standards, often the smaller our market due to price
As a crude example, an increase in minimum wage, could see increased EU immigration, but in other areas see jobs relocate to other parts of EU
As you approach full employment, its often likely that more people will flow in to fill roles, so often EU countries with high living standards get high migration which leads towards high youth unemployment. Over 30% of 18-25 year olds in Spain, Italy are unemployed, it was 40% 18-25 unemployed in Greece when I last looked
This ends up creating a skills gaps for young workers, and the more talented ones tend to emigrate, as the economy struggles