Accounting Tags for Expenses

Hello!

We are considering setting up accounting tags for our expenses module. I have a few questions:

1) Can accounting tags be used in classic and fluid? For example, we will use the fluid expense report creation page, but the classic travel authorization page.

2) When doing the accounting tag registration, is expenses grouped under the "Payables" Owner Object ID? Or do we establish the Owner Object ID?

3) If we register Payables so that our expenses module can use accounting tags, does our accounts payable module also have to use accounting tags?

4) Are we able to do a mixture of speedcharts and accounting tags? Or is it all or nothing?