I've been fiddling with this for a while, and I haven't found a "right" combination, but some mixes were very good vapes, at least for me.
I use menthol crystals. I fill a beaker 3/4th with finely crushed crystals and top off with PG. I place the beaker in a warm-hot water bath and stir until everything dissolves. I then use this mix sparingly in juices. About 1% gives a slight cooling effect, 2% a menthol feel mostly on exhale, 3%+ strong menthol taste, above 5% it gets nasty (throat burn, bitter aftertaste).
As for menthol-tobacco, my best achievement (I'm new to this so it might be lame) is 2-3% of my menthol mix over a base of 2% VZ virginia, ~1% either TPA Bittersweet or Capella "Snick-Snack" and 1 drop / 10 ml of TA. I vary things a lot between mixes, so this is just an approximate. Basically I'd play with a "super-concentrated" mild tobacco flavor, a pinch of TA and some nutty / cocoa-ish / bitter note... Hope it helps, as tastes are so subjective. I see people use this "Seedman's commercial cigarette", but I never got it yet...
Another thing I like a lot is menthol + FA peppermint + EM or marshmallow (but that's more like candy-cane than menthol cigarette, lol)