Passive income cannot be the basis for the contribution. It is common to mistakenly believe that contributions to retirement plans can be based on total income (i.e., earned income from work plus passive income), but this is not true. Retirement plan contributions can only be based on earned income subject to FICA and Medicare taxes. The contribution limits of your SIMPLE IRA plan are independent of the limits of your SEP plan.
Assuming that you don't also own your employer's business, you can make the most of both plans. Most people who work in the sharing economy will qualify to open an SEP IRA because they earn 1099 in income from NEC. If you still can't choose an SEP IRA, an Individual IRA (k) or a SIMPLE IRA for your company, you can use any of these top online brokers to help you open an account. You can usually choose between a traditional IRA, a Roth IRA, and an SEP IRA for retirement contributions.
The funds you (not the employer) contribute to an SEP IRA will reduce the amount you can contribute to your other IRAs. This means that your company may be operating in a poor economy the same year you are expected to make greater contributions to a defined benefit plan.