Final answer:
The Virginia Plan is the proposal that wanted Congressional representation to be based on population. It suggested a two-house legislature with the lower house based on population, contrasting with the equal representation for each state proposed by the New Jersey Plan.
Step-by-step explanation:
The proposal/compromise you are referring to that wanted Congressional representation to be based on population is the Virginia Plan. The Virginia Plan proposed a bicameral legislature, which meant it would have two houses. The lower house's representation would be based on the population of each state, and the upper house would be selected by the lower house from candidates proposed by state legislatures. This proposal was favored by the more populous states because it would give them more influence in Congress.
In contrast, the New Jersey Plan advocated for a unicameral legislature with equal representation for each state regardless of population. The Three-Fifths Compromise dealt with the counting of enslaved individuals for representation and taxation purposes, not the structure of the Congress itself.
And the concept of Separation of Powers refers to the division of government responsibilities into distinct branches to limit any one branch from exercising the core functions of another. The ultimate decision was the Great Compromise, which combined elements from both the Virginia and New Jersey plans, leading to our current system where the Senate has two senators from each state and the House of Representatives has members based on state populations.