New to 3D printing and have questions

The R1+ "needs" nothing in terms of upgrades out of the box. When something breaks or needs replacement, then consider upgrading it.

Well, generally speaking, the resolution of the print changes. There is a rule-of-thumb that layer height needs to be 30%-70% of the nozzle diameter. [the default nozzle is 0.4mm and the default layer height is 0.2mm -- smack in the middle] If you consider the nozzle diameter the width of the plastic you are putting down then layer height is the 'height' or tallness of that layer. So obviously as those numbers go down or up the size of the layers will change and there will be more or less granularity. Does this really change things? Somewhat. To really see it'es effect you would need to go from one extreme to another. Smaller layer heights allow you to do finer resolutions an smaller prints with more detail (but at slower speeds). Larger nozzles and layer heights mean a bit less resolution but much faster print times.