Consolidation onto Exadata Cloud_at_Customer on premise cores-->OCPUs

I'm trying to figure out what my OCPU requirements will be if I migrate from:

non exadata / non multitenant --> exadata cloud_at_customer (includes multitenant)

I've heard from one exadata customer that you can expect a 30-40% reduction in db compute cores needed. I anticipate that multi tenancy will help the reduction of CPU cores needed as well. I understand that the gains realized will depend on types of workloads and other factors. I'm hoping others can share their experiences with regards to cpu core reduction (for different workloads and overall) and also general experiences with exadata cloud_at_customer. All feedback welcome and appreciated!

some background:
I work for a municipality. We are an Oracle and SQL shop and have 2 DBAs, each of which wear many hats.

For Oracle we have:
a mix of 11.2.0.4 and 12.1.0.2
both Oracle Linux and Windows - ODA's and HP servers some standard edition
enterprise edition plus partitioning and some RAC

We have roughly 25 oracle databases, and are about to kick off a big project that will add 5 more databases. We foresee growing by another 5-10 databases over the next few years. Our workloads are diverse and the majority of our databases are under 200G, with a handful that cross into a few TB.

We keep buying hardware to satisfy different licensing combinations. Our leadership is not comfortable with moving workloads to the public cloud and it must remain on premise. We have a new system coming on board with significant Oracle hardware and licensing requirements, and I thought perhaps this might be an opportunity to pick a solution that would enable us to consolidate across the organization.

I want to consolidate, not worry about licensed options anymore, make patching easier with less downtime (2 dba's, many hats), have room for growth over the next 5 years, and have the TCO be the same or better than the traditional HW/SW approach we have now. For the TCO I can't assign a dollar value to things like better up time, improved security, time saved through easier administration, all packs are included, etc. Finance folks will reject those numbers.

We've explored a few different consolidation options: