You have essentially described the current US Senate/House as it was originally set out in the constitution.
One group of limited seats, with equal seats per state (the Senate). This is the "guarantee of at least X seats" to each state part.
A second group with the number of seats determined directly by population (the House). This is "the rest set ... according to census data on population".
One big change along the way was an amendment that capped the size of the House at 435 members to avoid it growing ever larger as the population expanded. Now the 435 are allocated to the states based on population.
> One big change along the way was an amendment that capped the size of the House at 435 members to avoid it growing ever larger as the population expanded. Now the 435 are allocated to the states based on population.
Thankfully, the Permanent Apportionment Act is not actually a constitutional amendment and could be corrected with the passing of legislation rather than needing to go through a full amendment process.