The main reason for documenting the two types of installation is because, when you are only measuring currents where you know the direction of power flow, it’s not absolutely necessary to have the a.c. adapter. So the Type 1 doesn’t need the a.c. adapter because you know the P.V. will only generate (well, neglecting its ‘keep awake’ overnight drain) and the house will only consume; whereas the Type 2 does because without it, you can’t know whether overall you’re importing or exporting.
(DIsclosure: Amazingly, I don’t have P.V., so I’m writing this from an Electrical Engineer’s point of view, and not from an installers’.)
I would opt for connecting the P.V. infeed as close to the meter as possible (Type 1 cabling), and not feed in via a consumer unit that supplies the rest of the house. I’d even put my own isolator between the grid meter and the Henley Block. It just seems so much cleaner and more “controlled” that way. Plus, you can measure whichever pair of quantities you like (not necessarily Type 1 monitoring) - and change your mind later if necessary. If you don’t have either Type exactly, it means you might need to change the software slightly from the ‘standard’.
True, due to one of the most elementary laws of electricity, you only need to measure two of the three quantities, but errors and inaccuracies can have a bearing. Say for example you are subtracting¹ two almost-equal powers, but they’re both subject to (say) a 1% error. If they are within 1% of each other, the calculated quantity could be wrong by a huge amount in percentage terms - even the wrong sign (= direction of power flow).
I think it comes down to which quantities are you most interested in, that you want to know with the least uncertainty.
¹ Note: That includes adding a negative value!