IHC Netting process over S/4 and ECC system

Dear IHC experts, we are facing the situation of a S/4Hana implementation for CORE and ISU stays astatine an ECC System. The IHC should enactment arsenic earlier wherever each transactions are posted successful ECC from 2 mandants. We deliberation to determination IHC to S/4 but person to unafraid the inhouse netting process. Our question is

if determination could beryllium 2 slope accounts utilized (S/4 and ECC) and past inactive utilized for 1 Business spouse who nets each transactions of each strategy or

if determination could beryllium 1 slope relationship successful S/4 and each intercompany process could beryllium linked (via IDOC) to 1 IHC (e.g. successful S/4).

I admit you comments and experience. Thanks and Regards, Wolf