Is it safe to use this 60W PD charged for a late 2016 MacBook Pro 13"?
Generally speaking, using a charger with a lower watage rating than the charger that came with the device will just mean that the device will take a longer time to charge. As long as the charger delivers the correct voltage (which is set by the USB specifications) it will not damage the device. Thus, if you trust that the charger properly follows the specifications laid out by the USB industry group, it should not pose a danger, but could take longer than a "proper" charger.

Using a charger with a higher watage rating should also work, but has the potential danger of allowing the device to draw more power than is safe for the device. In this case you would need to trust that the device maker has followed good design process and limits the power that it draws rather than just taking the maximum that the charger can push out.

I trust Apple not to allow their devices to draw more power than they can handle, and thus often hook up low power MacBookAir devices to high power MacBookPro chargers.