I mostly work in controlled scraps and I have all sorts of rules for what can/cannot touch each other. I've said it before that while we want randomness, true random can result in ugly and so what I strive for is aesthetic randomness. Usually I am looking for some sense of movement or "meta" design with my scraps and not just random.
I've developed many techniques for achieving aesthetic randomness but recently I did a project with very few rules using fabrics I wouldn't ordinarily choose but got in a bag at the thrift store, my "Wonky Bright". 9-patch where other than all seams were sewn straight and each block did have exactly 9 patches, fabrics I wouldn't ordinarily let touch (like a green stripe and a green polka dot, or a green polka dot next to a purple polka dot, etc.) were allowed to fall where they may. It came out just fine, pretty much exactly as I visualized (a quilt too loud to sleep under!).
So this is my advice: Personally I prefer to do my scrappy by blocks rather than each block have each piece different I'd rather have coordinated fabrics for each block. But all over works too and I will be using it for an upcoming project even though I find it rather chaotic, it is what that project and that collection of fabric calls for.
If you are going to do an "everything in the pool", then make sure you have adequate representation of the different colors. If everything is very pale but a couple of dark pieces, love the dark pieces because you are always going to see them, or take them out, or add more to the mix.
People tend to like particular colors or styles and their stashes reflect that so their scrap projects are already pre-sorted. Sadly, my stash is a bit all over the place but I can tell you I have very little orange in it (even though I like orange just fine). My friend in Arizona works almost always in batiks so batiks is what she has as scraps.
What I've found is no matter how hard you try to keep two fabrics away from each other, they end up there in the end so unless it makes you physically sick to put them together, just go ahead and do it. Likewise, if there are only 4 pieces of orange in the entire quilt, somehow they all end up within the same square foot of each other.
Don't stress, have fun, and I have to give myself a time limit when doing layout. Good enough is indeed good enough. If I mess with it past that I find more and more issues.