Thanks for the reply.
I have the following settings for DNS
When turning on the WG client (the correct client device is chosen in VPN Policy area)
All DNS lookups continue to occur through the local pihole at 192.168.1..252 instead of using the DNS servers of the VPN provider specified config
I have tested with "Allow Custom DNS to Override VPN DNS" turned off and on, and it is the same outcome.
Current FW is 4.7.5-op24, the problem was still there previously on 4.6.6-op24 also.
Client/s receive DNS server settings via DHCP, and the DHCP server settings are below.
Any thoughts are greatly appreciated.