If you want to run your own recursive DNS server, why would you run two separate DNS servers?
I’m not sure I understand your question. A recursive DNS server and a local DNS cache/forwarder/are two different things with two different purposes. You will always need both. You yourself are using AdguardHome and that is just connecting to recursive DNS server upstream. In my scenario you’re just running both yourself instead of you running one and then letting a 3rd party run the other for you.
Your outbound queries will still be unencrypted, so your ISP can still log them and create an advertising profile based on them.
You can encrypt the recursive queries through your ISP if you want to. Though the effectiveness of any profiling your ISP would do to you are minimized by Qname minimization that Unbound does by default.
If you’re just using DoH then you’re just shifting who’s making that advertising profile on you from your ISP to whoever is hosting your upstream recursive DNS server. It doesn’t matter how much encryption you do because on the other end of that encrypted connection is the entity who you’re giving all your queries to.