Does it make sense to use parallel activity?

Parallel: you have two or more parallel flow that are executed at the same time. While it might not be exactly parallel it’s close enough.

It’s actually not that useful in RPA, especially if that part of the flow involves UI elements. Yes, you can enter 12 values in 12 fields into a form and gain a second or two in performance, but as soon as any pre submit processing is involved in the UI, which is more common than you think, you’ll run into all kinds of exotic problem. Always consider that a UI is designed to function for 1 user using 1 keyboard/mouse as input, effectively doing everything one by one.

As for the pick branch variation, this one is a lot more useful. The only parallel component of this set of activities is that it checks multiple conditions at the (roughly) same time, and as soon as it has a hit on a specific condition it will follow that flow and ignore all other branches. Ideal for detecting multiple conditions during searches and login sequences. The conditions used are mostly activities like ‘element exists’ or one of its modern variations. Best to check the UiPath documentation for their exact usage.