Radiant ceiling is nothing to worry about - it typically isn’t all that powerful, meaning you don’t get much for capacity. 2x4 panel is ~0.5kW or so normally. Baseboard is going to get more out.
Radiant is different than convective (baseboard). Baseboard works by heating air, and then it rises and mixes in the space. Radiant heats by heating objects in the space. The space itself can be cooler, because your perceived comfort is higher when your accepting heat radiantly - think about standing in the sun on a cold day. Those panels work the same way.
And as far as the efficiency - electric is pretty dang good and converting to heat, like has been said. But as far as a heat pump comparison, refrigerant boils at a really low temperature and the ability to leverage that makes it quite efficient, more so than electric resistance. Even when cold, refrigerant can pull energy from air outside air, and the r cycle can release that inside (reverse of normal ac) to give you heat.
As far as heating the whole home with elec radiant. I’d agree with above poster, not ideal at all, and I’d expect to do an upgrade at some point. Radiant is great but those panels are just nice for spot heating little places or specific locations, not an entire system. Depending on where you live, the system options for “what’s best” might differ. And if you’re upgrading, I would highly encourage you to look at getting some ventilation incorporated into your system.
Never thought any of that would even come up on Rokslide ha ha - got any questions feel free to PM me.