I compared all the apps I regularly use (Messenger, Facebook, Discord, PlayStation Messenger, Xbox, etc.) to my 6s+ and the XR for about 30 minutes today and I didn't notice any blurring in the text. It looked the same crisp and clear on both devices to me. So far the only icons I've seen that look blurry are in my banking app. I even toyed around with making the text larger and smaller and I didn't notice any blurriness on my 6s+ vs XR.