I find the info in the ANONYMITY_NETWORKS.md document to be somewhat opaque and the cost of misconfiguring your anonymity network could be high.
I wouldn't use the term "opaque", rather they are detailed and expect a certain level of competence. There's really very little "cost of misconfiguring", rather things just wont work if misconfigured. At worst you will be just using a node like you currently do, over clearnet, and at best, working correctly broadcasting txs over anonymity networks.
Under what conditions would you choose add-exclusive-node instead of add-peer?
This is more a monerod question than an i2p/tor question. Here is the help on those options:
--add-peer arg Manually add peer to local peerlist
--add-exclusive-node arg Specify list of peers to connect to
only. If this option is given the
options add-priority-node and seed-node
So you see, they have different purposes.
Where the question relates to i2p/tor comes into how the tor/i2p integration works - quoting the documentation:
Only handshakes, peer timed syncs and transaction broadcast messages are supported over anonymity networks. If one --add-exclusive-node p2p address is specified, then no syncing will take place and only transaction broadcasting can occur. It is therefore recommended that --add-exclusive-node be combined with additional exclusive IPv4 address(es).
Hence, to allow your node to broadcast transaction over tor/i2p you can
--add-exclusive-node <tor/i2p-node>, but then if you also want the same node to be able to sync blocks (over ipv4), you also need to
"If configured properly, additional peers can be found through typical p2p peerlist sharing." What is the proper configuration that achieves this?
Configured properly, meaning you have configured for outbound tor/i2p connections (e.g. set
--tx-proxy and added one or more tor/i2p nodes).
Does this mean you specify one anonymous peer manually and it will discover the rest?
If you connect to another tor/i2p peer that also has connections to other tor/i2p nodes, yes, you will receive peerlists which include other tor/i2p peers.
Where does one find a list of peers to add manually? Is the one given in the document a real one intended for use, or just an example?
One can run their own tor/i2p peer by following the documentation for inbound connections. One of the things we hope to do (largely for the single-click GUI users use-case answered in your other question), is have a few community run/maintained seeds which operate on tor/i2p. This removes the need to run your own tor/i2p node, though just like with standard remote node usage, places a certain amount of trust in those remote nodes.
Does one need anonymous-inbound if you're only running your node locally and connecting to it from a local wallet, or is anonymous-inbound necessary for participating in the p2p network?
--anonymous-inbound is necessary if you plan on running a full node that is made available to other node/wallets over tor/i2p. This maybe your own node on a VPS server which you plan to use over tor/i2p and/or make available to other users who need access to a node over tor/i2p (like the example peers available to GUI users mentioned above).