How would primary and secondary insurance work in this scenario?

Hello everyone! Looking for some guidance. I live in PA and was offered a job which would require my husband to take his own health insurance from his employer. He would be able to use my insurance as secondary. This is quite different than the job I have now which allows him to be on my plan without him having to take the insurance offered through his work.

His plan is PPO HSA 2750. His annual deductible is $2750. Maximum out of pocket is $6,900. Preventative care is covered without reaching deductible, but everything else, including prescriptions, requires him to meet his deductible before the plan would pay.

My insurance is Choice PPO. My annual deductible is $800. The deductible only applies to certain services like X-ray, surgery). Regular and specialist are only subject to copay ($20). Prescriptions are covered at $15 copay for generic

If my husband had a claim, how would it be processed? Would he need to meet his deductible before my insurance would process the claim? He is on 4 generic prescriptions every month. How would these be processed? It seems under his insurance we would need to pay the full retail cost of the prescriptions until he reaches the deductible. Under my insurance, it seems that each would cost $15 copay.

Any guidance you could provide would be very appreciated! Thank you!