Please see our documentation for explanation of diferences bwteeen tallyLCA and tallyCAT. In a nutshell: tallyLCA is a A-D whole-building LCA tool covering multiple environmental impact categories, tallyCAT is a A1-A5 upfront carbon tool covering only fossil GWP (at the time of this thread - we’re working on updates). tallyCAT is a Revit plugin, no need for BIM360.
The reason you cannot add EPDs to tallyLCA is because EPDs lack info for calculating some of the other life cycle stages and environmental impacts in a consistent manner across all the possible EPD data sources. Any EPDs in tallyLCA have always been “re-modeled” by the provider of the GaBi LCA data to ensure consistency in background data and assumptions. This is a very tedious and inefficient process so we are working on some changes.