VPN on router and/or pi-hole

Hi,
I have changed my ISP router for something more customisable, then flashed openwrt on it and set up pi-hole on a raspberry pi. So far so good and it does block a good share of connections from local devices such as smart TV and radio and Bae’s devices. Mine are using a VPN so they’re not really affected.
But, if I get things right, my ISP still sees traffic from our home (outside of my devices). With the view of generally minimising the amount of data we give out, would you recommend setting up a VPN on the router, perhaps for devices not already using one locally? Would this run alongside pi-hole or negate any point of pi-hole?
Thanks!