I've been using a software called Synapse Audio Orion Platinum.

The question is, SAOP offered a drum sampler which allowed me to go into a piano roll mode and manually input what I wanted it to play (which was quite useful since I do a lot of Metal-style drums with double bass drums and all).

So, does Session Drummer 3 that comes in X1 offer that as well? like, go into piano roll and manually compose stuff so I can make it sound like x2 bass?

Thanks!

While Session Drummer does not have a double bass drum, you could assign a second base sample to one of the percussion pads, so I think the answer to your question is yes.

Yes its very easy :)

Just pretend theres a double kick pedle on the kickdrum ;) and then put the notes you want in piano roll