can you pay from apple savings account

No. Apple Savings is not liquid, not immediately available for direct payment. You need make a withdrawal from there and into your bank account or Apple Cash and then use that to make a payment. Transfer to bank account typically takes 1 to 3 business days.

click here ➜ Set up and use Savings in Apple Wallet - Apple Support

Excellent - just did a small amount test transfer - works as directed into Apple Cash from Apple Savings - instant. I wish this was made clear when I signed up for this banking system. Not a problem, but an non-intuitive convolution...