You may have to fiddle with it again when you put in your hardscape as items such as logs and rocks could impede flow.
On the tank on the tank I've just started I did run the Co2 system before I put anything in but that was only to ensure everything was working as it should and had no leaks.
I'd wait until you've got your hardscape in before fiddling with the drop checkers, also bear in mind that once plants grow in, these could also affect flow to certain areas in the tank depending on size and position etc.
When making adjustments to you Co2 and drop checkers make them slowly ( very slowly ) in can take up to 2 hours for the colour to reflect any changes and even then it's only showing you what these levels were 1-2 hours ago, patience is key here.
I have 2 at the moment so I can change them around at night and check their readings when I get in from work the next day.
I would think that if everywhere is getting Co2 then everywhere will have nutrients as well providing your dosing the column with a fertiliser.
A Nutritious substrate will not only provide vital nutrients to root feeders but will act as a buffer till you get things just right. (for ferts that is).
I also have a bottle of easy carbo which I am using in addition to injected Co2 till I know I've got things right, but liquid based Co2 products can harm certain plants.
I'm also a scaping noob and all of the above is based on some of the experience I've had and information from this site, I'm sure that one of our experts will fill in any gaps I've left.
Hope this helps
