How much does resource quality really matter?

Solution 1:

In short: yes. A T1 item made with high-quality materials should approximately match (if I'm not mistaken) a T2 one made with low-quality stuff.

Somewhat longer: gear is made of subcomponents. Each of those subcomponents' quality increases a single attribute of the final piece from its base attributes. For example, a rifle barrel will probably affect damage per round, while a magazine will affect magazine size. Higher tier equipment will use more subcomponents and thus allow for greater overall customisability, and also have higher base attributes.

Also keep in mind that using higher-quality materials will increase an item's power and mass requirements, so you may want to use more basic materials for subcomponents you consider less important.