"So ideally you'll run with the bow in quite a high attitude?"
No not really. Whilst it will depend on the boat and engine, the average RIB will be running quite level on the plane. As you transit from displacement to planning, you climb over your own bow wave and during this you may find that your bow lifts.
However, once over this, your bow will drop again and your now planning = speed increases rapidly with no more application of additional power.
At this point input babs of trim and listen and feel for increases in rpm/speed, note the trim angle. Keep doing this until either the RIB begins to feel unstable or the prop begins to cavitate, at which point trim the engine back in to the last angle it felt right. You will now have a better feel for what is right for your setup.
Do all this at lowish speed (3000rpm ish) so that if anything happens that you do not like, you still have control.
As said before though, I would strongly recommend doing at least the PWB level 2, with your own RIB, you will learn so much.