which option is better regarding integration between BTP subaccount access and IAS

[hopefbest1]

<scenario>

Currently, customer has subscribed one BTP global accounts. they would like to access various subaccounts through IAS according to requirement, so we need to activate the IAS for BTP subaccounts.

We are currently implementing Successfactors (SF) system, and have created the IAS per SF instance to access SF through IAS, with the relationship SF:IAS=1:1; At the same time, We enhanced several  Fiori applications in BTP for SF system, and set up SSO between SF and BTP in order to directly access these Fiori applications through SSO from the SF side. Now we would like to activate IAS for BTP as well so that we can access both SF and BTP through IAS.

<Confirmation>

For integrating the IAS with BTP, we understand that IAS tenant is created per Subaccount, because we have created IAS tenants per SF. which is better between creating new IAS per BTP subaccount and using the existing IAS of SF? or is there any other better solution? Can you give me some suggestions? Thank you.

1. For BTP subaccount, we do not create a new IAS, but still use the existing IAS created by SF. Attachment ①

2. For BTP subaccount, do not use the existing IAS created by SF, but create a new IAS . Attachment ②

In addition, we can now access the Fiori application on BTP from SF by configuring SSO. If we use the attachment ② solution, because SF and BTP use different IAS, Is there be any problems affecting access to Fiori application? Please help confirm.

best Regards.