Super basic, paper and sellotape.
Basic, blank white labels sold with adhesive.
I make less than a thousand with different lots flavours & strengths and share them. Thermal transfer printer on thermal labels single colour labels, simple but will do the job.
I make a thousand a month, but with a few different flavours and strengths, I also have artworks. Short run label services.
I want to sell them, short run label service making sure I'm getting polypropylene using a thermal printer for at least the strengths maybe the flavours until my volumes get bigger. Then buy a tactile warning label and hand apply them.
I make and sell thousands of each flavour and strength. Get a professional printer to do it for you, these volumes should get some good prices now. Let them be concerned about labels and you about making e-liquids.