LG Q6 Plus SAR value is as follows:
SAR Value (Head): 0.72 Wkg@1g
SAR Value (Body): 0.455 Wkg@1g
Yes, LG Q6 Plus does support Miracast.
LG Q6 Plus has 3000 mAh Li-Ion battery which offers talk time of about 16 hours and standby time of about 200 hours.
Yes, LG Q6 Plus does have the VoLTE.