Hi Jo - the register online and by post will be identical. They confirm the current registered owners only.
Other entries will refer to old deeds/documents for example but the actual ownership, B Proprietorship Register, will only refer to the current legal owner.
If you are looking for past ownership information you would need to use our contact form to ask the Q, explain what it is you are trying to find/establish. The support team will then advise what we have and how to then apply by post to get copies as appropriate
For example if you wanted to know who owned the title from 1986/87 right through to current then you can apply for a copy of each and every edition of the register where a change of ownership occurred
But you need to contact us first to allow us to check and confirm
Public guidance: dealing with land and property - GOV.UK