Tobacco flavors are all over the net. RY4, USA Mix (Marlboro), Virginia, Turkish, SEC (Kent), and many other including menthol flavors like Newport. Look and you will find!
Indeed! You'll need to experiment (e.g., using sample-sized bottles) to find the flavor(s) and variations you like the best.
Somewhat oversimplified (and not addressing PG vs. VG), there are two categories: China-made (mainly DeKang) and USA (or U.K.)-made. The former is cheaper; most people think the latter tastes better.
Unless a supplier specifies otherwise, the juice they carry probably is China-made ... and I think many of the flavors taste pretty good. Dave mentioned some of them; I would add DK-TAB (DeKang Turkish-American Blend), RY3, Hilton, Flue-Cured, and Cuban Cigar.
I've read/viewed glowing reviews of the USA-made tobacco juices from
Halo (e.g., Freedom),
Alien Visions (e.g., Boba's Bounty),
VaporBomb (e.g., Maxboro Ultimate),
Viking Vapor (e.g., Cherry Smoke Tobacco), and
liquidXpress' Honey Flue Cured Tobacco.
I've found candre23's sortable
Cost Per ml + Shipping Chart of e-liquid suppliers very useful in identifying the least expensive sources.