I'm looking at getting the Xperia X Performance. It has two slots for SIM cards. Will the phone work alright with only one normal SIM and will all the apps still work ok? A long time ago I red most apps don't work for dual sim, but I'm not sure if this has changed. (if this question is too specific, feel free to answer it for any phone)
user manual for your specific device does not mention such restrictions and it also gives out the combination of SIM networks permitted when both SIM's are inserted, so there is no reason to believe app restrictions whether you use one SIM or both
PS: My device is Moto X Play normally used with one SIM but works fine with both SIMs
You won't have any problems if you insert only one SIM into dual SIM phone, i have dual sim phone myself with only one SIM in it and it work without any problem. Phone will work even you don't have any SIM in it.