The aim of this investigation was to analyse the external workload, tactical individual actions of passing, and perceived internal load during unbalanced small-sided games. Ball possession formats (4v3, 4v4 and 4v5) were played in three different playing area dimensions (20 × 15m, 25 × 20m and 30 × 25m) by under-23 football players. Data were analysed under opposition-based perspective, by fixing one team (4vX), and by cooperation-based perspective according to teammates (4v2+X) for each playing area condition. GPS monitors were used to collect and compute external workloads (distance covered while walking, running, sprinting, and maximal speed) and tactical individual actions (passing with dominant and non-dominant foot, and maximum passing speed), and Borg Scale CR10 to evaluate rating of perceived exertion (RPE). On both opposition- and cooperation-based perspectives, significant differences were found on external workload variables for all game formats, with smaller areas associated with more distances covered while walking and larger areas with running and sprinting. Likewise, 4v3, 4v4 and 4v2 + 3 revealed significant differences for tactical individual actions, where a larger area was associated with an increase in repetitions. Medium playing area, for both perspectives, was associated with a higher RPE. Overall, larger playing areas with higher number of players involved promoted more high-intensity running, while the same area with fewer number of players fostered tactical individual actions. Smaller areas allowed to reduce game pace, especially in formats with fewer players. Different unbalance scenarios under dissimilar playing area dimensions promote diverse performance outcomes on player’s action capabilities.