Do printouts of individual pages of seforim, or small [sections of] seforim which were only meant to be used once or twice, have to be put into shaimos? Why or why not?

Minchat Yitzchak 1:18, which is a continuation of 1:17, says something printed with intent to be disposable [eg. newspapers with divrei torah or galley proofs] can be thrown out. He has a number of reasons, but at the core of his argument is the Rambam in Avot Ha-tumah 9:11 that the parshat sotah is not metameih [just like sifrei minim are not metameih] one's hands because it was written with intent to be disposable and he cites a source based on a Yerushalmi that that's the reason there's no violation of the issur of erasing God's name, since it was originally written with intent to be erased.

Is an ordinary Chumash metame*? Can it be thrown out?

*I'm being facetious.

It's not so facetious - take a look at the Igerot Moshe OC 4:39.

the way i see it done, is that if a copy is made butnot used,it can be thrown out, but if it's used, it's shamos.

Hows that work?

I'm going to guess that it's the "galley proof" argument: Once you use it, it's no longer disposable - it was printed to be used and therefore not printed with intent to be disposable. It's sort of a retroactive characterization in that once you use it, you have demonstrated that it wasn't meant to be disposed of, rather it was meant to be used. And once it's used, it gets a kedushah of sorts and is elevated. As opposed to either printed something off on your computer to see if the alignment and pagination is correct, which is meant to be disposable, or as opposed to printing off 20 copies of something which you only end up needing 15 copies of.
But that's just a guess.
It's sort of in a sense like people who think that the glass jam jar doesn't need to be toveled, the jar the jam comes in from the manufacturer. But soon as you finish the jam completely and re-use the jar for jelly beans, it's no longer disposable. OK, it's not really like that.