You can only use option 2, there's no way to "borrow" quota from one user and assign it to another. As to option 2, its best to switch to a license which includes "unlimited" quota.
How to increase onedrive storage

I have a very small business, with just two employees. We have a M365 account with two licenses. Each license comes with 1 TB of OneDrive storage. I need to increase one person's storage. The following two options are the only ones i can think of, but I cannot find a way to do it in the admin center: 1. Decrease the low user's storage to 500GB, and then add their other 500 GB to the high users's storage, bringing the high users up to 1.5TB. 2. Purchase/Add more storage to the company's subscription. But preferably add it all to the high users account and none to the low users account. Any help on how to do this would be appreciated. Thank you.