user-1: What is the maximum number of outbound full relay connections a bitcoin core full node can make?
I was assuming it's 8 but then realized we can add another 8 connections using addnode while reviewing this PR: https://github.com/bitcoin/bitcoin/pull/21710
So is it 16 or there is something else that I am missing which can be used to add more outbound full relay connections?
Also do we have any option to decrease the number of MAX_OUTBOUND_FULL_RELAY_CONNECTIONS below 8?

user-1: 
What is the maximum number of outbound full relay connections a bitcoin core full node can make?

Maximum number of outbound full relay connections is 16(8 automatic and 8 manual)
MAX_OUTBOUND_FULL_RELAY_CONNECTIONS 8 (automatic)
MAX_ADDNODE_CONNECTIONS 8 (manual)
If you add 8 trusted nodes with -connect option, those will be the only nodes used for outbound full relay connections and nothing else.

Also do we have any option to decrease the number of MAX_OUTBOUND_FULL_RELAY_CONNECTIONS below 8?

No. And the developers who reviewed PR: https://github.com/bitcoin/bitcoin/pull/21815  think we don't need such option in Bitcoin Core.

-1: <p>What is the maximum number of outbound full relay connections a bitcoin core full node can make?</p>
<p>I was assuming it's 8 but then realized we can add another 8 connections using <code>addnode</code> while reviewing this PR: <a href="https://github.com/bitcoin/bitcoin/pull/21710" rel="nofollow noreferrer">https://github.com/bitcoin/bitcoin/pull/21710</a></p>
<p>So is it 16 or there is something else that I am missing which can be used to add more outbound full relay connections?</p>
<p>Also do we have any option to decrease the number of <a href="https://github.com/bitcoin/bitcoin/blob/66fd3b28e85c167f3955b5603496daf8d91abcad/src/net.h#L64" rel="nofollow noreferrer">MAX_OUTBOUND_FULL_RELAY_CONNECTIONS</a> below 8?</p>
 -1: <blockquote>
<p>What is the maximum number of outbound full relay connections a bitcoin core full node can make?</p>
</blockquote>
<p>Maximum number of outbound full relay connections is 16(8 automatic and 8 manual)</p>
<p><code>MAX_OUTBOUND_FULL_RELAY_CONNECTIONS</code> 8 (automatic)</p>
<p><code>MAX_ADDNODE_CONNECTIONS</code> 8 (manual)</p>
<p><em>If you add 8 trusted nodes with <code>-connect</code> option, those will be the only nodes used for outbound full relay connections and nothing else.</em></p>
<blockquote>
<p>Also do we have any option to decrease the number of MAX_OUTBOUND_FULL_RELAY_CONNECTIONS below 8?</p>
</blockquote>
<p>No. And the developers who reviewed PR: <a href="https://github.com/bitcoin/bitcoin/pull/21815" rel="nofollow noreferrer">https://github.com/bitcoin/bitcoin/pull/21815</a>  think we don't need such option in Bitcoin Core.</p>
