When importing SVG to Inkscape, I notice that some CSS styling of text is ingored (text-transform:uppercase / font-size:larger). I can't tell if the other stylings are implemented (font:14px / font:sans-serif / text-anchor:middle / dominant-baseline:central) or not. Is there a list of CSS styles that are supported, and are there any inkscape-specific tags that can be added to the SVG to aid their implementation on upload?

The CSS stylings are implemented, you can test by opening the Object>Selectors and CSS dialog. 

Speculation: text-transform: uppercase might not be an SVG supported presentation attribute, although some renderers like browsers may recognize it.  https://www.w3.org/TR/SVG11/attindex.html#PresentationAttributes.  Not sure about font-size: larger... it may require a parent element to be relative to. https://www.w3.org/TR/2008/REC-CSS2-20080411/fonts.html#propdef-font-size

For an authoritative opinion, I'd ask the Devs on the chat: https://chat.inkscape.org/channel/inkscape_user