I need some advice

I just ordered the 29UM58 IPS LG and I'm very excited. I've mostly ordered it because of Flight Sim's. I still have my old monitor in a working condition ( Samsung S23A700D ).

Now since both of the monitors are 1080p I'm left to wonder if I can use them both when gaming if I create a custom resolution? Is this the resolution I should use 2560 + 1920 = 4480x1080p?