building SP in one's account also earns them enormous amounts of voting weight, which is dependent on the amount of SP staked

You are right . More vite weight would inturn yield more curation rewards .

There are three steps involved in curating content in steem Blockchain.

You have given comprehensive account of curation within the three headings. Commenting on posts is also part of curation through which we can add value to the task or even we can ask doubts, if any to add to knowledge.

Good luck