Firewalla gold + dns config?

with the free dns resolvers from controld on my firewalla router

do i need to use the Secure Resolvers with the Legacy Resolvers for any of the offered options to have them work well

i want to use the & as my primary & secondary dns options for the wan input on my FWG (firewalla gold)

would doing so work the same as when using just the secure version or do you have to use both together to get the full benefit

or could i mix an match by using the uncensored dns legacy resolver on my firewalla router wan input an then use the from Ads & Tracking in the custom doh server settings , is ther any benefit or draw-back in doing this ?