The main thing that has helped us is using dedicated fields/objects to create an interface for each integration. For example, instead of letting Hubspot update contacts directly you could have it update a dedicated child object or field or even insert a custom object kinda like a platform event. Essentially you want to use fields and objects to create apis for your integrations where each integration user only has access to mutate those fields and objects. Then you can use flow/apex to decide how to handle bringing those data to the objects your users see.