Flexibility involves the adjustment of energy consumption or generation schedules to benefit the grid, for instance, providing services such as balancing, congestion management, and voltage control. Flexibility can be offered at different grid levels by flexibility service providers (FSPs) through market mechanisms. This study, produced in the context of the Horizon 2020 OneNet project, evaluates various TSO-DSO coordinated flexibility market models. In this assessment, the study considers factors like economic efficiency, consumer-centricity, existence of entry barriers, and value-stacking potential. The analysis highlights the importance of interface flow pricing and FSPs' bidding behaviour. The creation of local market layers can reduce entry barriers but may lead to market fragmentation. The study also explores bid forwarding mechanisms and methods to ensure grid safety. Overall, the work offers valuable insights for designing efficient and coordinated flexibility markets in Europe.