Execution only PRSA process

I don’t have an occupational pension and planning to start my pension journey through an execution only PRSA. I can manage to make decisions about the funds, brokers and contributions. But I’m not sure what services are in the scope of the execution only brokers and have few queries on how exactly the process works in real life. If anyone has gone though a similar process it would be helpful if you can enlighten me.

1. ⁠Once we setup a Regular contribution account can we make additional lump sum contributions as and when we like? Are there any minimum limits/extra charges for this?

2. ⁠Who handles increase/decrease/switch funds once it is setup?

3. ⁠If in future we don’t want to be with the broker but not change the provider, what options do we have?