The free version of bots such as gekko and zenbot does not have any special features unless someone shares automated strategies that can be used for backtesting, but there are no strategies that you can implement to these free trading bots. Paid bots, on the other hand, do have some feature to copy other traders' strategies or use other built-in strategies that you can later backtest and use if you get better results.
I am not sure if bots are necessary, but if you do not know how to use them, you could lose all of your funds. You should avoid using them because they will not help you make a profit unless you have a target price. However, I believe you do not need those software because most exchanges now have bots.