What do you think is the difference? They appear to be synonyms to me
The object of the prepositional phrase is "the several states", not the people of the several states. Big difference.
The point of that power was to allow congress to regulate commerce among the states. For example, to make laws against state tariffs or quotas.
I'm still seeing a distinction without a difference. Interstate trade refers as you say to that the federal government can prevent States from creating as you said tariffs or quotas or restrict certain products. Government can regulate the movement of goods and services when moving between the States.
The intent was to prevent barriers to trade, but they did just give them the power to regulate it generally.
What material difference are you seeing in "commerce among the several states?" I'm not arguing with you, I just don't understand the difference you are claiming
The material difference I see would be that any law congress passed to implement this power would apply to the states, not to individuals.
I agree with that the restrictions apply to the States, not individuals. But can you give me an example how in a practical sense those are different? Tariffs between States for example would be a restriction on individuals by the States with the Federal government saying States can't restrict individuals that way, so I don't see an actual difference.
A current practical situation is the Federal government should strike down a lot more barriers to trade, like forcing you to buy your car from a dealer (which adds $1K-$2K) to the price of a car and prevents you from buying say directly from Ford. It's a car, why can't you just buy it from Ford? Medical insurance is huge, the Feds can and should strike down restricting us from buying medical insurance from out of State insurers.
So yes, the Feds in those cases are restricting States, but it benefits individuals. I'm not clear how the end effect is different