The API documentation of the exchange and Python [some searches on github] would solve and automate the most common trading needs free of charge.
Paid bots should make it easy for the user to add/adjust functions and provide enough support.
The pre defined methods are most of the time only there as start point.
Yes, it is good but it still need a manual setup for it to function properly. You also need to monitor it because its performance is not that stable because it is a bot. ... It still needs proper management because it is an automated so you need to still guide on how it deals with the market.
Depends which bot you choose. Arbitrage bots would probably run out of the box but could be expensive.
Most bots will help you with the monitoring part by notifying you when things go out of order or to assure you things are going right.
When using boundaries management will be allot easier.