In Britain, a loaf of bread would generally be anything big enough to be cut into multiple slices of bread, e.g. for making sandwiches. So this is a loaf, and at least the one on the left of this picture is a loaf.
The items in the second picture that are small enough to be just 1 - 2 portions, would be rolls. Buns tend to be sweeter than rolls, although a soft roll containing raisins and currants is often called a currant bun.
Normally, bread is an uncountable noun. Having said that, searching Google for "three breads" does give many hits. Specifically:
- "Three breads" may be used to mean "three types of bread", e.g.:
Salmon and Scrambled Egg with three breads here
BLT choice of three breads, mine was a baguette here
- The term is used biblically and in sermons, etc., e.g.:
“Three Breads” - John 6:24-35 here
- There appears to be a place in New Zealand, named "Three Breads & 2 Fishes"
The search also revealed a forum discussion here on the subject "How to ask for two 'breads'", which included the following comment:
Sorry, but I have never heard anyone say "2 breads" when 2 loaves is meant.
The only time that "breads" could be used, is if different types of bread is meant.
I have to buy three breads: a loaf of gluten-free for Rose, two loaves of sour-dough rye for Daisy, and a white loaf for Hyacinth.
I'll leave others to search further if desired.
To address the final sub-question, "Can the word servings be used?":
One can talk of "servings of bread", but the items in the picture would not normally be described to in that way.
The expression "servings of bread" could be used in a restaurant, but its meaning would depend on how the restaurant serves their breads. [I have intentionally used the plural there, which I think is acceptable in this context.]
A serving of bread would be the amount of bread that the restaurant normally serves for one person, such as two slices of bread; one bread roll; a few bread sticks; etc.. You would refer to three rolls as "three servings of bread" only if the restaurant normally served one bread roll per person.