You have full control over which clients see or do not see the option to use Joist Payments.
You can turn the default payments option on or off, which would determine whether or not each subsequent estimate or invoice you create has payments enabled.
You can find this option in iOS by tapping More in the bottom right corner, then Payments Settings; in Android by tapping Manage, then Payments Settings; On the Web, go to Payments from the menu on the left side of the screen. You can then enable or disable the "Accept Credit Cards and PayPal on new documents" option.
You can always choose to turn payments on or off on a specific estimate or invoice using the payments switch in the Edit screen for that document -- this choice affects only that document.