[Drako]

Of course there will be traces of something hidden if you're encrypting a bootloaded operating system. It won't matter if it's solid state or a spinning drive. What you want is plausible deniability on a wiped drive that just has data on it, and no operating system.

And yes, if you're buying a laptop you can replace a HDD pretty easily. The SATA and power will work just fine. Though like you said, I highly doubt a modern gaming laptop will come equipped with a HDD instead of an SSD.

But I'm not entirely sure what you're trying to say at the end. It sounds like you want a HDD over a SSD?