Which is a good option for configuring the Deployer with Smart Target, i.e. a separate Deployer or use the existing
Deployer/HttpUpload for the website?
In the most common scenario you would use the existing Deployer. Having an extra target means users have to double publish / unpublish from two additional targets, plus there is the overhead of maintaining extra targets (consider upgrades etc).
Also consider content is dynamic and can come from the Broker. So if a user only publishes to ST (and not the broker) there could be an issue where the identifier from ST is returned which then returns nothing from the broker.
I'd rather the publishing fails in both site and SmartTarget in the event of failure.
Business requirements will likely dictate the publishing architecture, and there may be specific scenarios where one may want to have separate targets. Tridion is flexible enough to support both approaches.