The banjo bolt on the pressure line at the rack is a 19mm I believe, I use a chrome swivel socket to get at it. Pretty sure the low pressure one is also a 19mm. Really do not pay much attention, as I have them all, I just grab the one that fits.
The banjo bolt on the pressure line at the pump is 22 or 24mm. The return hose at the pump is just a constant tension clamp, same as those on the reservoir.
I would use an OEM quality fluid, yes. We use Pentosin 11S here.
There are also a few 13mm head nuts and bolts that hold various brackets on t he high pressure line, which are in different places depending on the transmission. Manuals are easier, as they go under. Automatics go over.