Wether online or offline you need to ensure that your seed phrase is very tight and secured wherever it is, because if you recommend people to safe it offline if proper care is not taken they would still end up disclosing it to people in some cases it might be your love ones that would disclose it to people not you, so if you choose to store your seed phrase offline you need to keep it out from the reach of people. And one thing is that our seed phrase is not supposed to be stored in one particular place is good to save it across other places to avoid One particular point of failure, Because your seed phrase can get missing some day and without you storing it across other places you will just end up losing the whole assets.