In Blueprint ,create a value in a Actor to ref other Actor is like pointer in C++?

I means the value which ref other Actor can be null?such as the refed actor have not be Spawn in game?the Null ref need how much Memory size?

All memory references (pointers) are the same size, and that size is dependent on if it’s is 32- or 64-bit application. If it’s a 32-bit application, memory references are 4 bytes, and for 64-bit applications, memory references are 8 bytes.