Your school system provides you with a list of 403(b) companies. The 457 plan is different. The city/town usually provides one company. Both typically give you a broad range of investment options.
SEPs are supercharged IRAs, following the same rules but allowing for higher contributions. In 2020, the self-employed can contribute the lesser of (a) $57,000 or (b) 20% of their net adjusted income (gross income from self-employment minus expenses and half of one’s self-employment tax).
Most of the 41 states with state income taxes conform in some way to the Federal Tax Code. For example, Colorado uses the federal definition of taxable income to figure state taxes owed, and taxable income is one’s income after all deductions. This means any Colorado taxpayer who loses deductions and exemptions at the Federal level also loses them at the state level. And, unlike the feds, neither Colorado nor any other state has reduced its tax rates to reflect the broader tax base.