Hi and welcome, regionalised means we added more regions to flows than ecoinvent (e.g., there may be some unit processes from Spain with water input, and in the original ecoinvent, these water input flows are "global", we changed this to Spain in this database, so that is better characterised in some impact methods. LCI is the system process database version which you normally do not need unless you want to have a very small model. Decide for one option, you do not need to merge all in one (or, shouldn't - LCI and unit processes can make sense, if you want to do this, start from the LCI database since this is much bigger.
The databases contain our LCIA method pack already, but we also provide the ecoinvent version for those interested, this is the original release by ecoinvent (transformed to work in openLCA). Hth, Andreas