not sure what you mean by "nontoxic",,,I think alot of things we use are probably toxic,,,glue, etc,,,,
as far as acid free goes, I try and use ALL acid free, simply because you never know WHAT it's going to do,,,,,HOWEVER, I've used some things that are acidic, I'm sure,,,,cardboard, etc,,,many people do, and yes, the most IMPORTANT thing is that it doesn't touch your pictures,,,or that you spray it with archival spray before you use it,,,
If you are concerned about archival quality, do NOT use acidic items on your page. Acid migrates (or travels), so it doe not matter whether it's touching your photo or not. Over time, it will deteriorate.
Of course, there is acid in your skin, so if you are being "truly" archival, you would wear gloves while scrapping, which I doubt anyone does.
This is a personal choice.
I try to use mostly acid-free items on my pages. If I find something I want to use that is not acid-free, I will typically use it anyway.
Although, I will never use fun foam or construction paper, because that stuff will break down in a matter of months!
As for acid neutralizing sprays. My opinion is that they are extremely expensive and haven't been around long enough to test whether they actually work.
I figure that if a small percentage of my pages do not stand the test of time, that's okay, I have plenty of others!
It's a matter of choice as it's been said. But uf you're going to spend the money on good supplies, you'll probably want to keep it acid/lignin free as much as possible. For example, acid free adhesive--why use otherwise when it's readily available and does make a difference. Likewise paper. You know newspaper yellows and degrades fairly rapidly so it's better to photocopy or scan it. Or if I really want to incorporate the original, I'll spray with a sealer rather than a de-acidifier. I'll never use a pvc plastic since it de-gasses, nor plant materials like real flowers, or rusty metal. I'll probably not use leather either,( avoid heavily alkaline stuff also). But fabric and ribbons?--sure--ubless it's acetate! Buttons? Yup. They don't say acid-free but I know it's okay.
If I know something is acidic, I'll avoid it. (Most inkjet transparencies are made in an acid bath, for example.) If I can find a readily available alternative I use it. If I have to use something and I'm not sure, then I probably will use it...unless I suspect it's going to degrade or cause other stuff to degrade.