I have a question
A node is needed to execute a transaction, but in which node are these wallets connected to execute a transaction?
all wallets are tied to a node? or can that specific wallet be connected to a chosen node or a public node?
for example, daedalus downloads a whole node, so I might guess that the transaction is running on the same daedalus node, but yoroi does not install any node on the user's pc, so where is that transaction sent to be validated?
You're correct - Daedalus runs a full node on the local PC, so transactions initiated on Daedalus are submitted through the local running node. The same is true for transactions submitted using cardano-cli or cardano-wallet - they use a locally running node.
For other wallet software(s) like Yoroi, Nami, etc that are browser extensions, they submit transactions via remote nodes administered on some back-end servers.
I can't speak for yoroi, but nami is another light wallet. It interfaces with the chain using the blockfrost api. This handles talking to the nodes.
Nami now lets you point it at a node of your choice https://twitter.com/pernistoken/status/1485563609560551428
Other light wallets do something analogous.
