Hey guys, I hope you all have been well.

I don't know much about computers, so I apologize in advance for the noob questions, but I would really appreciate help/opinions if anyone has time.

I am trying to decide weather to pick 16 or 32 GB of RAM for my Alienware desktop

It is the HyperX 3200 Mhz.

I'd prefer just buying 16 GB and adding more myself, as it is a lot cheaper that way.

My questions though are.  The 16 GB or RAM option is a single channel 16 GB stick.

The 32 GB RAM is "Dual Channel", so it is 2 16 GB sticks?

So if I choose a single channel, 16 GB option, and after I get the computer buy 1 more 16 GB stick, will that make me have Dual channel 32 GB of ram, making it the same as if i picked the 32 gb option when buying the computer? Or since I chose 1 single channel 16 GB stick, and buy another one myself and add it, it wont be dual channel and not as good?

Will it be faster buying the comp at 32 GB dual channel, compared to  buying 16 GB single channel, and adding another 16 GB stick? Or is it the exact same thing?

Sales rep is telling me otherwise, and it wont be as fast that way. I think because he wants to sell me the 32 GB one.

Sorry for the noob questions but I don't know much about computers and I appreciate your time and help guys.