i am not sure so experts opinion is required here.
afaik 1 accor is 1.8 rupee and 1 mariott is 0.3p [sometimes more depending on the property where you burn your points]
For accor booking you can book with 2k points…and do call the ibis where you are going to stay to know about the taxes and other services, can they be settle with accor points at the time of checkout or not.
As much i read in forums some one mentiones the redemptions are in multiple of 2k points [ was 1k few months back also]
P.S Do correct will happy to learn more ..