The classification of sprays with isotropic curvature is a central theme in spray geometry. In this paper, we investigated a class of spherically symmetric sprays—those invariant under spherical rotations. First, we derived a necessary and sufficient condition for such a spray to have isotropic curvature; the condition was a system of differential equations. For the important subclass of projectively affine spherically symmetric sprays, we then obtained the corresponding equivalent system of partial differential equations (PDEs). Furthermore, we constructed several explicit sprays of isotropic curvature.

Without the quadratic restriction, there are many non-Riemannian geometric quantities in Finsler geometry. Among these geometric quantities, Berwald curvature, Landsberg curvature and mean Landsberg curvature are related directly to the famous "unicorn problem" in Finsler geometry. In this paper, Finsler metrics with vanishing weakly Landsberg curvature (i.e., weakly Landsberg metrics) are studied. For the general $(\alpha ,\beta )$-metrics, which are composed by a Riemannian metric $\alpha$ and a 1-form $\beta$, we found that if the expression of the metric function doesn't depend on the dimension $n$, then any weakly Landsberg $(\alpha ,\beta )$-metric with a conformal 1-form must be a Landsberg metric. In the two-dimensional case, the weakly Landsberg case is equivalent to the Landsberg case. Further, we classified two-dimensional Berwald general $(\alpha ,\beta )$-metrics with a conformal 1-form.

The $E$-curvature is one of the most important non-Riemannian quantities in Finsler geometry. In this paper, we study Finsler warped product metrics with isotropic $E$-curvature and constant $E$-curvature. The equations that characterize Finsler warped product metrics of the above $E$-curvature are given. Moreover, some specific metrics with isotropic $E$-curvature are constructed.