You can use both monitors with this mount as it is designed for two monitors. However, the maximum monitor size for this mount is 34 inches, which is suitable for your 34-inch curved monitor, but the 27-inch monitor should also be able to be mounted without any problems. The mount offers a maximum payload of 20kg, which should also be sufficient as most monitors weigh less. To mount both monitors horizontally, you need to make sure that the VESA mounting points of the monitors are compatible (75 x 75 mm or 100 x 100 mm).