Grasslands NP is tremendous! I have not been there since we got our trailer (13' Boler; intend to upgrade to an escape) but we intend to go back soon. Boondocking is the way to go there!
Cypress Hills in the southwest is a gem. Pine Cree is a small regional park that gets lots of raves. We were going to go last August ... but a choice between 37 C or 27 C weather sent us to near Hinton instead.
Most provincial parks near Saskatchewan cities and large towns are setup for the mega-RV set. Sometimes good fishing but not much for scenery. Yawn.
My favourite location is McDougal Creek in the Narrow Hills Provincial Park. Two camp sites, a pit toilet, and a short walk to a creek with brookies. Nothing fancy except silence and isolation. A short distance away is Clarence - Steepbank provincial part - maybe 8 sites, fishing and not much else. Paradise
No mountains ... but they get in the way of the view anyway!