You can't complete overall north east within 7 days . try for assam and meghalaya...
day 1 reach Guwahati and take a taxi to shilong. book a car for next three days to travel Meghalaya and night stay at sohra.
day 2 visit cherapunjee and night stay at cherapunjee
day3 visit double decker bridge and dawaki lake and stay at mawlinlong which is aisa's cleanest village.
day 4 visit shilong and directly come to kamakhya... stay near the kamakhya temple.. don't plan to stay at shilong..
day 5 do puja at kamakhya temple which is one of the shakti pith of India and start your journey for kaziranga forest stay at homestay in kaziranga
day 6 jungle safari and night stay at Guwahati.
day 7 vitit on bahmhaputra river and small islands on the river.. take flight or train at evening.