Complicated, still unsure if you mean you are growing some of both types on the one bed.
Say medium peas one end, two rows across the 1.5m width of bed @ 6in gives 10 modules per row, 20 altogether.
Then tall peas at other end, one row of 10 modules, across the 1.5m, about 6in from the end of the bed. This allows a fairly wide space in the bed’s middle. You could plant some lettuce or spinach to use that before peas get big.