Case 1 sounds like NC, Major renovation. Case 2 would likely be NC if the remaining 70% is to be occupied by the owner in the future, since they will control the build-out. If that remaining space is to leased to other tenants who will control their own tenant improvement build-out, then the project would be Core and Shell. Look at CS Appendix 3 in the BD&C Reference Guide for guidance on how to define the finished/ unfinished spaces.

Since these answers depends a lot on percentages of project area that are effected by different scopes of work such as finishes, HVAC, and envelope, the most useful method we've seen is to walk through LEED Online v3 as if you are registering the project. There's a "wizard" that walks you through a number of questions if you indicate you want help selecting a rating system.

There are a couple of tables that help chose the proper rating system, but it can be hard to find them unless you work back a forth a few times answering the questions differently to test different scenarios. We've often found it helpful to cross reference the Glossary in the MPR Supplemental Guidance document and the Reference Guides as you do this to verify you're using the proper definitions of key terms such as "major renovation," "alterations, " etc. You may also need to consult the EBOM Reference Guide for definitions of additions and alterations of existing buildings.