Can I accept two funded offers from universities and decide later after April 15?
No, you cannot do this.

According to the April 15 Resolution of the Council of Graduate Schools, you cannot accept multiple award offers simultaneously. You are not committed to any offer signed before April 15, in that you can submit a written statement declining a previously accepted offer. But you cannot accept multiple offers before or on April 15, and changing offers after that date requires a written release from the school with whom the offer that was “in force” on April 15.