I’m sorry for off topic, but candles can also be dangerous to a cat; it’s a little smoke for humans, but cats are smaller and it can be enough to cause some respiratory issues if exposed regularly (my cat has asthma so I’m rather paranoid about that ). Also, when she was a kitten and we boarded her with our friends, she burnt her whiskers when going too close to the candle...I can always use candles to deal with any odor and I can always vacuum the bits that get out of the box. The odor control for So Phresh is fine. I can't smell pee at all and it's only when my boys drop a turd that I smell anything at all. In which case I light a pet odor eliminating candle (you can find these on chewy.com) and scoop it out.
As for litter, I’m using SmartCat and SoPhresh grass seed interchangeably; it’s little difference between the two to me imo. But I noticed that SoPhresh is better when bought online, they pack it in a tight box, whereas when I was picking it up from Petco, it happened to me that it was more dusty then usual. But I live in a city and it doesn’t have to travel a lot, it’s delivered from the same place so I guess transport doesn’t affect it a lot, it can be different if it would need spend days in a truck I think.
I also tested almost every non clay litter on the market and settled with grass seed - it’s not perfect, especially it’s tracking is annoying, but it’s best when it comes to dust and it’s most important to me. Clay litters scare me to my bones and I’d never try them on my cats.