lovinit, you say '"From my observations, she really does seem uncomfortable ... legs pulling up and a kind of throat clearing noise that does not stop as if something is bothering her ... "
If she is soothed and comforted by a feed, then I would say these signs are merely telling you she wants to feed/be cuddled. Babies of four weeks old cry if something is really botherng them.
If she seems more comfortable upright, then hold her that way! Some babies devcelop preferences for being in a particular position rather than others. I don't thnk it's a big deal, or worth puzzlling over, to be honest.
"Do you not think that I should try and encourage her to take the other breast as well to make sure she doesn't just snack ? "
By all means offer it, because she can't 'ask' you in words. She may or may not take it.
"What are your thoughts on snacking babies and how it is actually not healthy for them to for digestive reasons ? "
I don't have any thoughts. I can't see why taking food in in smaller amounts if this is what the baby seems to want is not healthy. How would it impact on her digestion? How do you know what is a 'snack'? You can't tell if the baby has had a large or a small amount by looking at the clock. In pre-industrial societies, when babies are held all the time by their mothers (as there is nowhere safe for them to be put down) babies feed dozens and dozens of times a day (and night). No one counts them, or times them. Certainly, no one frets about snacking. This is the way we have lived for 99.999 per cent of human existence. Breastmilk and breastfeeding evolved in these conditions. It is not possible that it would have evolved to be 'bad' for the bab's digestion to feed often.
Western babies do not 'know' they are born in 2005 with cots and cribs and prams and worries about clocks and snacks. But they do adapt, and many are fine and well-fed on quite different feeding patterns. But you don't need to rush your baby into that pattern as she will become more predictable and patient anyway.
Anyone telling you that snacking is wrong for health reasons doesn't know much.
Unequal breasts are normal. It doesn't matter. You don't need to be worrying about equalising them!
Hope this helps.