Occupations on the CSOL can be nominated for a 457/ENS visa and can also be used for independent 190 or 489 applications providing you have the support of a State Government/Territory/Eligible Family member (as applicable). Occupations that appear on Schedule 1 of the CSOL (the SOL) are generally considered in high demand and can be used for an independent 189 Visa application.
ENS is a PR visa that requires a job offer (on-going for at least 2 years) from an eligible business. They can nominate you for a needed skilled position in their business (that appears on the CSOL) and you must meet the skill requirement for the position. Unless you've already been working for the company on a 457 visa for two years, the 'Direct Entry' pathway will be the way forward. For Direct Entry you will need to have your skills assessed by the relevant authority and demonstrate you have at least 3 years relevant experience.
I would say it's unusual for a company to sponsor a brand new candidate for an ENS visa. Generally in situations like yours a company would take you on first as a WHV holder for a probationary period, then 457 if things work out well, then ENS - Transition stream. Sponsorship carries a number of obligations so it's not something they enter into lightly.
All the best,