Hi ,I read some people arguing on lack of jump engines on Banu ?

But what are those and how many different types of engines are around?

Why a Constellation has very tiny engines and can go around charting the same as a Carrack that has a huge disk Ion Engine in middle of back ?
Why the engines od supposed same class of Banu are Abnormous huge?

how many different engines do exhist ? what are differences between them and whats a jump engine compared to another ? what a Ion engine etc?
Why on Carrack they have a disk shape and there is no disk shape on others apart Anvil ones?