bantams are just smaller. If they are all bantam they'll all be small. For reference, you could weigh the "Buff Brahma". At 1 week old my standard light Brahams weighed between 65 and 81 grams. If yours is much lighter than that at 1 week I would say bantam.
Number 4 looks too dark to be Delaware in my experience. The picture I shared in past two the light ones mixed in there are all light Brahma and Delaware. They looked identical besides the feather feet and comb for the first week or so.
1. Mixed, perhaps with a fibromelanistic breed?
2. Also a cross?
3. Buff Brahma
4. Columbian Rock, perhaps, or another mix.
5. Could either be a Barred Rock, or Cuckoo Marans, depending on leg color. When they're young like this, it's often difficult to accurately read leg color. Orange is universal on yellow and pink-legged breeds. However, I'm leaning towards Barred Rock.
ETA: There's a possibility the "Barred Rock" could be a Black Sex Link cockerel. Just another option.
