when i drifted mine, i dodnt bother with a locking diff etc, i just put some drift tyres on it and away it went, i did post a video on my micro rs4 thread (which i need to update)
you can buy a locking drive set, they arent expensive (one good thing about micros) but how much difference it makes, i honestly dont know, i have mine in grip setup.
http://www.ebay.co.uk/itm/HPI-73419-SOLID-DRIVE-SET-MICRO-RS4-MICRO-DRIFT-KEN-BLOCK-/322411751062?hash=item4b113ce696:g:v2oAAOSwOVpXc6~Y
with regards to lipo, im the wrong person to give advice, mines on an exoteck chassis so im limited to 800mah 2s batteries.