Yes that's correct. Didn't see any rangers.
I’ve climbed Whitney FOUR TIMES, and I’ve NEVER seen a ranger (let alone had my permit checked). Then again, I’ve never gotten an alpine start, and I’ve never done it on a weekend. So maybe that has something to do with it. I’m guessing that rangers are probably going to be out there more during popular climbing times.
I happen to be of the school "I'd rather do it in one day than haul the camping gear", but I believe you are more likely to summit if you do camp.
This depends. There is more that makes backpacking difficult than just the heavy pack. There are also training issues, sleep issues, food issues, and bathroom issues (among other things) to consider. Problems with any of these things can ruin your day and send you packing back to the Portal. And they are more likely to happen if Whitney is your first backpack. Backpacking clearly works better if you are an experienced backpacker. But the average person who hikes Whitney probably isn’t. Many have likely never carried a heavy pack on their back. And many people train for Whitney by doing other long dayhikes (think San Gorgonio via Vivian Creek, White Mountain Peak, or Red Slate Mountain vis McGee Creek). People who train like this are basically set up for doing a dayhike (and not a backpack). This doubly so if the person in question has never backpacked a day in their life.