The floor model of the combi-boiler has a 15 US gallon buffer, for the domestic hot water, the wall hung has only 2 gallons.
This model only has a 5:1 turn down ratio, which can be a short-cycling issue at condensing temperatures if you don't have enough radiation on each zone to emit the full min-fire output at condensing temperatures. Before diving in on these run the napkin math on both your
whole-house heat load, and
your radiation. At condensing temps the min-fire output is about 26-27,000 BTU/hr. It takes at least 125-130 feet of fin tube baseboard to emit that much heat with 125-130F water.
The bigger-burner WBRCNG199F (W) has a 10:1 turn down, and can drop back to about 18-19,000 BTU/hr, which can be emitted by 90-100' of baseboard @ 125F-130F water.
The same combi boilers can be had under the HTP nameplate as EFTC-140F (W) or EFTC-199F (W), which may be better supported in your area than Westinghouse. My understanding is that HTP is the importer, and Westinghouse buys them from HTP. Same equipment, different support chains. They are designed & manufactured for export by a first-tier Korean boiler company, Kiturami, a company that competes head to head with Kyung Dong Boiler (Navien) at home, but has taken a different North American marketing strategy. I believe Laars (Canada) carries them too, which may or may not be better supported than Westinghouse in Ohio. (Laars HQ is right across the lake from Ohio.)
The related HTP UFT-xxxW modulating condensing boilers seem to be popular & reliable in my area (New England), but distributor & installer support varies regionally. ( HTP's HQ is in Massachusetts.)