Well, these workflow choices are pretty much a tradeoff between keeping the highest possible quality and saving on disk space and to some degree working memory.
If the Photoshop work you want to do is "serious editing" then you will typically be using layers and, at some point you will need to decide how much of your layers work you might want to keep, so you can revisit your project and maybe readjust things or whatever. In this case you will have to save as a tiff or psd. An 8 bit would be fine for minor adjstments but if you foresee having major adjustments to do a 16 bit gives you more latitude to adjust without image degredation.
Of course, it's these tiffs and/or psds that are monsters in file size. And this is where the tradeoffs go: you may flatten the layers in a file -- this will save both file size and working memory, but of course at that point you no longer have access to the original background layer without bringing in the original Raw file, and you also won't be able to revisit. But, if you are comfortable with the work you've done, it's an option -- the tiff or psd will be significantly smaller than one packed with layers.
And then is the other option, which is to declare the project "done" and also to decide you will not want to revisit it and also that you only want to save for a particualar output. You can convert it to a jpeg, after doing whatever size and sharpening tasks need to be done. If you are planning a print, well, you'd want a full res high quality jpeg.
You could alternatively actually produce two jpegs, one for print and one for the Web/sharing/presenting, taking care to keep one process separate from the other so they don't mess each other up.
So, my suggestion -- open a Raw image directly in Photoshop. If you are using Lightroom, the Edit in Photoshop function will create a tiff or psd (according to your preferences) and will automatically import that in your library. When you Save (not Save As) in Photoshop those saves will go to that file. Make the workflow choices above -- If you end up not wanting the huge file, well, delete it. I've done that. Just don't delete it unless you've thought over the work you've done on it and as to whether you really do want it to go away!
I personally only go to jpeg for a final output.