It depends on the type of transactions, but to make it easy, simple transaction size is ~250 bytes, with most of it is signature. From what I understand, if we assume SegWit transaction size of 100 bytes, then 1Mb block can contain 10k transactions, or roughly 16 tx/s. (or more realistically 14 tx as you said). SegWit doesn't increase the block size to 2 or 4Mb, it just leaves separate space for signatures, and that is where up to 4Mb comes in. Pretty much you can only have up to 1,000,000 bytes standard block, but you can have some extra space where you add witness data.
It depends on the type of transactions, but to make it easy, simple transaction size is ~250 bytes, with most of it is signature. From what I understand, if we assume SegWit transaction size of 100 bytes, then 1Mb block can contain 10k transactions, or roughly 16 tx/s. (or more realistically 14 tx as you said). SegWit doesn't increase the block size to 2 or 4Mb, it just leaves separate space for signatures, and that is where up to 4Mb comes in. Pretty much you can only have up to 1,000,000 bytes standard block, but you can have some extra space where you add witness data.