Adding a high voltage shield to a traditional low voltage product invites all kinds of issues.
The small relay's ratings are further obscured by putting them on a board that begs "go for it". Having used relays in the past for switching line voltage, there is no way I would buy one of these since the pedigree of the parts are fundamental to the quality of its future operation.
Do any of these project boards have Nationally Recognized Test Laboratory markings? It isn't mentioned and it should. Since it has line voltages on the board, shouldn't the board be manufactured to a higher level? One false move an it's all toast. Shouldn't the boards come pre-buttered?
In working with high voltages myself, it is very important to know that the traces have sufficient spacings for contamination, voltage separation, and current handling without overheating the PCB material.
While the projects are cool, working with those voltages on an open frame design is dangerous. The arcing shown for fun on the project page is closer to reality than you think.