I wouldn't recommend a pi zero to run a browser, as you say its under powered.
The kiosk option would work well on an RPI4, however they are not easy to come by these days 
Using the standard dashboard - You can display a background image of your choosing via some CSS.
Locating the readings at specific locations is not that simple, but it could be done with some thought to the layout.
There is also node called node-red-contrib-ui-svg
With this you could create any layout you want, take a look at the wiki for some ideas.
Not sure what your skill level is, but if you can draw something in Inkscape then you can overlay interactive elements / text / graphics etc quite easily. (This may be the quickest option for you)
Failing that there are a couple of alternative dashboards you could look at -
node-red-contrib-uibuilder or flexdash these offer more flexiblity than the standard dashboard.
