There are concentrations of Brain Trees throughout Guardian space. Area A1 isn't unique. What is unique is that I've catalogued the contents of these systems' biological and geological locations for you.
So by visiting the seven systems on the Harvest Tour you can find all the raw materials you need for synthesis and engineering (except for those three materials that can only be found when laser mining).
There are also Guardian Structure sites in the area. You can find Module and Weapon blueprints, Guardian manufactured materials, and "Obelisk" data while you're here.
But you won't find everything: Area A1 contains no ruins and no Vessel Blueprint sites. To gather Vessel blueprints or lots of "Obelisk" data you're still better off down below, in the main Guardian area.
If you visit every biological and geological location in all seven systems on the Tour, you'll build up respectable stores of these raw materials. You might even fill up your storage for all of them. (I did! But I visited many more locations in the area, too.)
If you complete the Tour and you still want more, you could top up the rest by consulting the full list of Brain Tree sites in the immediate area. I've catalogued them all within a roughly spherical area that's about sixty or seventy light years across.
I've also added optional side trips where you can pick up some Guardian data, materials, and blueprints. These are just a couple of the Area A1 Guardian sites I've described here.
Although I've picked other bodies as better sources for its materials, the next moon over also has Brain Tree and geological locations. You can visit it, if you like - but the mountainside locations are a challenge.
Are you gathering Guardian materials and Blueprints up here? Consider dropping by HIP 41730 to visit its Weapon Blueprint site.
If you're gathering Guardian blueprints during your Tour, you'll want to visit the Module Blueprint Structure that's also located in this system.
Although I've picked other bodies as better sources for its materials, this system has another planet where you can find a small number of Brain Trees and geological locations.
Are you going straight back to the Bubble? Here are some more Brain Tree sites on your way there. But they don't represent a single route: they're gathered from several trips back and forth.