Office365 for iOS is a highly cut-down single install App intended for iPhone. It does not replicate the functionality of the individual Microsoft Apps intended for iPad and iPhone - Word, Excel, PowerPoint, Outlook etc.
For iPad devices with a screen larger the 10.1”, the MS App’s for iPad require an active Microsoft 365 Subscription; without an active subscription, functionality is limited to opening and reviewing existing documents.
As for considering an iPad instead of a computer - perhaps intending to have either one or other device, but not both - you need to consider this choice with considerable care. Whilst iPad is an excellent companion device, despite some creative marketing, iPad cannot yet provide the flexibility and functionality of a full laptop computer. You should also consider that some maintenance and recovery procedures (such as a system restore - or recovery from a lost or disabled device passcode) require access to a PC or Mac computer.
I hope this information and insight proves to be helpful in your decision making process.