Solid intro. One pattern worth adding: when you're reaching for Rc<RefCell<T>> for graph-like or self-referential data, an index-based arena (Vec<Node> with usize "pointers") is often a third path that keeps you in plain-ownership land — at the cost of pointer identity and some bookkeeping. petgraph, slotmap, and most ECS libraries formalize this. Doesn't replace Arc for genuinely cross-thread shared lifetimes, but it eliminates a lot of cases where people first reach for it.
The Vec approach can also have a nice benefit in terms of memory usage if you construct a lot of small structs (say, a linked list-style structure with a value and a forward reference). Rather than using 64 bits for a pointer, you can store an 8/16/32 bit number, depending on how many items you need. If the stars align, it can also help with keeping more items in the CPU cache lines.