Yes, LG V30 Plus does have the QUAD DAC which you can term as much superior to Dolby Atmos.
Yes, LG V30 Plus can record 4K videos very easily as the rear camera has the highest video recording resolution of 3840 x 2160 pixels. You can also record 4K videos with Hi-Fi audio recording.
Yes, Vivo V30 Plus is a VoLTE mobile phone.
Yes, LG V30+ does have the OTG support.