Could i use the MP2491C with a current limit of 1A. Or do I need to set the limit at least to 1.5A?
Welcome to the MPS Technical Forum. I would recommend you keep your current limit at or above 1.5A as shown on Page 8 of the datasheet.
Additionally, the MP2419C is 6A device. If you would like to set a 1A current limit, I can assist you in finding another converter better suited for your current specs.
You can probably set the limit to 1A with a resistor value high enough, but it won’t be very accurate. Especially the board to board variation should be quite large.