Around one year back, I was going through the same, building my 220G, with my first time into sump, and zero knowledge on overflows, pumps etc, leave alone BeanAnimal. So I must tell you, it will look like lots of unknowns, but its not that difficult.
To make things easy try to find readily available overflows that support either Herbie or BeanAnimal system. ESHOPPS is one option, as what I know. Holes needed on the tank, based on the available box. Rest of all information is readily available, and lots of help too.
And reg the pump, along with the capacity, see the noise levels for the pump too, since noise is one criteria. when you go for a silent system, and then pump is noisy, you know what i mean. I run a EHiem submersible pump in my sump, its decently silent.