"Each home is different so we can’t give specific savings amounts, but I would experiment to find the optimum settings for your house."
Whether or not you gain anything at all with setbacks is mostly a function of how tight & well insulated the house is, and the amount of thermal mass inside the thermal & pressure boundary of the house. Low-mass leaky houses cool off faster, reducing the delta-T between indoors & outdoors, which reduces the rate of heat flow out of the house. But a tight higher-R house with some amount of interior thermal mass (like maybe a radiant floor slab?) will almost never hit the setback limits, with very low, sometimes unmeasurably low reductions in fuel use. If you saved 3% in heat loss by going to setback, but lose 3% in efficiency on the recovery ramp by firing away at a higher temp you've gained nothing, and perhaps lost a bit of early morning comfort.
The raw efficiency of a mod con is determined by the entering water temp coming back from radiation, and the firing rate of the burner. With most the sweet spot on the firing rate is at or near the lowest modulated range, and going more than 50% of full fire cuts into condensing efficiency at any return water temp by a significant more-than-theorectical amount, which you'd somehow have to make up for with lower return water temps:
Setback is a better strategy with bang-bang cold-fired boilers and higher temp radiation, where standby losses can be reduced by letting the boiler cool off, and the efficiency curve is in the long, linear fairly flat non-condensing zone, where the firing rate is what it is, and the combustion efficiency not much affected over a 10-15F return water range.