Nifty index funds recommendation

I recently opened ICICI nre/nro pins/non-pins all 4in1 account. I have couple of lacs in nre as well as nro back account. I want to invest in index fund as I don't have time to actively track stocks. I understand each institution had there own index fund to track nifty. I plan to split 20% small cap, 50% mid cap, 20% large cap. My horizon is at least 5 year or add long as 15-20 year unless I have emergancy to withdraw. I am looking for advice which types of index are good interms of liquidiy, spread, etf mer fees ?