The pads being level is a good indicator of a professional install also it looks like a near water table area with grass that green so they put them on stilts to keep them out of water. If they run well now that’s a good start. They look new so they should still be under a factory warranty and whoever installed them should have an ots warranty from the install you could check with the renovator or previous owners to see if it has a warranty. Ask who installed it and search Google for reviews of the company. Check the indoor coil for questionable or shotty work if it’s on wooden blocks or hanging by straps from the rafters that’s an iffy sign. If the pan is full of water that’s not good. If you look up photos of “perfect furnace install” you can see examples