This paper focuses on planar manipulators built upon stacking a series of tensegrity X-joints. The manipulators are actuated with four tendons, have different numbers of modules, with or without offsets. The objective of this work is to study the influence of offsets and number of modules on the size of the wrench-feasible workspace (WFW). The comparison analysis is conducted on the basis of equal manipulator height, width and mass and of equal maximal actuation forces. The spring constants pf the X-joints are determined so that the configuration at rest features a C-shape at a given end-effector pose with a minimal stiffness to ensure stability. We show that the more the number of modules, the larger the WFW, and that the offsets have little influence.