The only difference between paper-based test and IBT test is: For paper-based test you are answering with 2B pencils and answer sheets, while the HSK iBT(at center), you would complete the test using a computer at a specific test center. And the HSK iBT(at home), you would complete the test at home(public areas are not allowed) with required computer/laptop and devices.

Paper-based test and iBT(at center), candidates should attend the test at specific test centers.