The role of citizens in the federal, confederation, and unitary systems differs in regards to the overall power of the individual. In the unitary system, power comes from the centralized government downwards. There is significantly less regional control in this system. A Confederation on the other hand potentially includes the most direct popular means of participating in government. As the state holds the most power, decisions would be directly determined by the eligible voters within the state. The Federal system is something of a hybrid of the two other systems. Significant power is vested in the Federal Government, but through the election of senators and representatives to Congress, citizens are able to have some input into their laws.
To my understanding, the division of power is what prevents one aspect of the state apparatus from becoming too powerful. Within our federal system, there are the Executive, Legislative, and Judicial wings of the government. Each holds separate but equal powers used to maintain balance within the system. The individual states also contribute to the division of power as a counterweight to the federal government itself.
The federal government plays a significant role in shaping state and local governments. Chiefly through the allocation of funds. One easy example of this is the drinking age. During the 1980s, the drinking age was set federally to 21. The federal government was able to compel lawmakers to agree to this by only providing highways funds to states that went along with it. And as federal law is the supreme law in the country, states are generally within standards set at a federal level. As we saw during COVID, the intervention of the federal government during emergencies can be massive. The federal government provided the state and local municipalities with supplies and funds to deal with the crisis. Obviously there were problems, and poor leadership at both federal and state levels made a bad situation worse, but the overall impact of the federal government during COVID was tremendous.