John Adams outlines some key points about different forms of government in a 3 paragraph summary:
1) Some forms of government are better suited to being well administered than others, and the form that brings happiness to the most people is best. Fear should not be the foundation of government.
2) In a large republic, it is impossible for all citizens to make laws, so power must be assigned from many to a few wise representatives. Elections must be fair to prevent corruption.
3) Separating government powers prevents any one branch from becoming too powerful. Elected offices should have term limits, and judges should have life terms subject to removal for misbehavior.