I just found this and this, if I understand it correctly, seems to say that the SEP is not limited by the 401K. What do you thinK?
https://www.irs.gov/retirement-plans/ho ... e-ira-planSIMPLE IRA plan limits
Employee contributions
You can make salary deferrals (salary reduction contributions) of up to $13,500 to a SIMPLE IRA plan in 2020 ($13,000 in 2019). If you’re age 50 or over, you can contribute an additional $3,000 (in 2015 - 2020) in catch-up contributions.
If you participate in more than one retirement plan that allows you to make salary deferrals (such as a 401(k) or a 403(b) plan), your total annual employee contributions to all the plans can’t exceed your personal limit of $19,500 in 2020 ($19,000 in 2019), plus an additional $6,500 in 2020 ($6,000 in 2015 - 2019) if you're age 50 or older. However, because the SIMPLE IRA plan limits your contributions to $12,500, plus an additional $3,000 catch-up contribution, this is the maximum amount you can contribute to your SIMPLE IRA plan.
Employer contributions
Your employer must either:
match your salary deferrals, on a dollar-for-dollar basis, up to 3% of your compensation, or
make a nonelective contribution of 2% of your compensation (taking into account no more than $285,000 of compensation in 2020 ($280,000 in 2019).
SEP plan limits
Your contributions to your SEP plan (that is not a SARSEP) are not reduced by the contributions you or your employer make to your employer’s SIMPLE IRA plan.
SEP plans (that are not SARSEPs) only allow employer contributions. For a self-employed individual, contributions are limited to 25% of your net earnings from self-employment (not including contributions for yourself), up to $57,000 (for 2020; $56,000 for 2019). You can calculate your plan contributions using the tables and worksheets in Pub. 560.
If your business sponsors another defined contribution plan in addition to your SEP plan (for example, a profit-sharing plan or a 401(k) plan), then your contributions for yourself to all these plans may not exceed 25% of your net earnings from self-employment (not including contributions for yourself), up to $57,000 (for 2020; $56,000 for 2019). Note that salary deferrals are not subject to the 25% limit and catch-up contributions are not included in the $57,000 limit.