I created a selection, filled it and put text on top of it in a 72 ppi file and copied the group to an image with much higher resolution. I transformed the shape and text to make it bigger. Does doing this affect quality? It looked ok, I'm just curious.
The filled selection sounds like a pixel layer. If its edges were sharp, scaling may have blurred the edges a little and non-horizontal and non-vertical edges may be slightly jagged. A vector Shape layer or a pixel layer with vector mask to define its shape will scale without edges being degraded by resampling when scaling. Type is composed of vectors, so as long as it was not rasterized before scaling, it will have retained good edges.
Vectors are resolution independant, so Shape layers and Type layers will scale without damage to edge quality.
However, there's a pitfall if you place the 72 ppi document as a Smart Object in a 200 ppi document. The SO will be automatically scaled to maintain its size in inches in the new document. The fact that it is scaled isn't a problem in itself since you'd be doing that manually if it wasn't automatic. But when the SO is scaled, the pixel representation of its embedded document (not the embedded file itself which remains unchanged) will be scaled and (non-destructively) degraded by resampling in the same way as a regular pixel layer would be.
You can avoid the SO scaling problem by opening the 72 ppi document, or a duplicate, and using Image > Image Size to resample it to 200 ppi. That higher resolution document can be used itself or it can be placed as a Smart Object in other 200 ppi documents.
By the way, characters of a given size of font will be rendered with slightly different forms in documents of differing resolution to maintain legibility despite increasing pixelation in lower resolution documents.
You can also resize the embedded smart object by opening the embedded smart object in Photoshop by double clicking on the smart object layer's smart icon in the layers palette. Photoshop will open the embedded smart object into a tepmorary work document. You then use Image Size to increase the size of the work document to the pixel size you need for the document your working on. Text layers will be update by change the font sizes, Shape layers are changed using vector graphics. Other layers will be interpolated. When you commit the document size change using menu File>Save Photoshop will save the temp file and the update the originale document embedded smart object to reflect these changes. You can then close the work document its no longer needed. The temp file that was save was saved into your user temp folder and will be deleted when the folder is cleaned up.