My question is if I accept two offers before April 15th and then get two i20s issued. It is up to me to choose the one university I want to go to and I am the one who has to complete the sevis formalities by mentioning the sevis id issued in one of the i20s, so from a legal standpoint, no one can stop me visa right?
I would not recommend to accept 2 offers and then later tell them "Oh, sorry guys I didnt mean it". This will certainly create bad blood and academia is in certain fields like a small village. In the worst case the other university could then withdraw their offer and you will not have single one.
Choose the offer that fits you better and behalf honestly.