If the babies have nice round tummies then they are being fed if they look rather skinny with lots of wrinkly skin then that’s a sign that they aren’t being fed... good luck!
I have no idea (I only do Flemish Giants) but I don’t think size matters that much - unless one is considerably smaller, it’s the tummies that show they are healthy and good size.
They look healthy to me! My 8 kits are all doing well, they seem to get a feed at exactly 8am and 2pm. Today is their 5th day, I’ll show pics this afternoon