Double coverage for IVF

I’m planning to do IVF starting in the beginning of next year. My husband and I are on our own separate plans but he is going to add me to his plan for next year, which will become my secondary plan. Hoping for insight on 1) how will billing work? For example, how would a $10,000 bill for IVF be applied?, and 2) is there anything else I need to consider? Is it a bad idea to keep the high deductible plan?

Insurance 1 (my primary) – Aetna HDHP. $3200 deductible/$4000 out of pocket max. $15,000 lifetime infertility coverage. Plan covers 90% after deductible. Does not cover injectable medication. I want to keep this plan because the premium is only $600/year and gets me the extra $15,000 towards infertility services.

Insurance 2 (my secondary) – FEHB BCBS standard plan. $700 deductible/$12,000 out of pocket max. $25,000 annual infertility coverage. Plan covers 85% after deductible. This plan does cover injectable medications. The COB for this plan says “After the primary plan processes the benefit, we will pay what is left of our allowance, up to our regular benefit. We will not pay more than our allowance.”