For a large electrolyzer plant, around GW scale (e.g., 300 to 600 electrolyzer stacks for hydrogen production), would you recommend installing local H2 vents for the stacks or routing these vents to a common large flare/vent system?

This decision would depend on the system design, system operation, and a hazard assessment. Likely it would be better to run all hydrogen vents to a common vent or flare system, but this might also restrict the ability to isolate smaller sections for maintenance.