The new 11 Pro and 11 Pro Max are just barely larger than the previous versions they replace, the XS and the XS Max. We’re talking like half a millimeter or so taller, wider, deeper. The 11’s are heavier, though, since they have significantly larger batteries. The lower end 11 and XR are equal sizes and weight.
There is a rumor that in Q1 2020 Apple will bring back a version of the lower cost iPhone SE that will be based on the 8 hardware, which is pretty much the same size as a 6s.
So generally speaking, the short answer is, no, it doesn’t look like iPhones are getting smaller.
One screen of apps?! Oh my. I have three screens of apps, then a fourth screen of just folders. I do have my most-used apps all on my first screen, though.