Lovely architecture and renders - well done.
How did you end up doing the grass?
Well, i spent many, many days in previous projects to find the best solutions with prepare good looki 3d grass. Why? Because i recognized that grass is alwyas filling up to 20-25% percent of my rendered pictures. These pictures above are good examples. Grass is always on first plan. And i made so many, many, tests with 3D grass which is in Forest Pack Pro library or with many other 3d grass models which i bought (3dmentor for example). And results were good but not superb good. 3d mentors grasses was one of the best solutions in many cases, but there i found this magic set:
https://gumroad.com/l/DAMA01Well it's not ready solution for all grass situations, but i made some my own mixes (layers for Forest Pack Pro) from that set and now i'm happy with result :) It looks beliveable:)
Greetings and i hope it will help You :)