I have been chasing clear cases for the iPhone 7 Plus for a while now. If you don't believe it, see the picture below. There are pros and cons to all of the cases.
1. Pretty much every clear case will turn yellow over time. The TPU has aromatic carbon rings in the polymer structure and these rings do break down with exposure to light - fluoroscent lighting is actually terrible for it.UV rays in the sunlight also contribute to the breakdown of the polymer which in turn leads to yellowing. Cheaper cases do not have any blockers added to them so they yellow faster than cases from reputable manufacturers but regardless of quality, the exposure to light or oxidizing agents (bleach or bleach based cleaners) will exacerbate and accelerate the degradation process.
2. You need to determine what parameters are important to you. Want a rugged case with lots of protection, want a crystal clear hard case, want a clear soft case, want some protection or maximum show off? Only you can decide what you want and then look through Amazon and read reviews (more detailed the better) and decide.
If you want help deciding once you have made up your mind about what things are important to you in a clear case (besides it being clear) feel free to PM me. If you want to try out a couple of cases, ping me, I can send some over for free if you cover shipping. I don't plan on using all of the clear cases that I have accumulated