Yes you still need PG and VG provided you use both to begin with....it will become evident why when you start to DIY with a calculator. ie , if you buy 24mg base of what ever PG/VG mixture and you add say 10% flavor (most are pg based)you would have diluted that mixture to where it is no longer 24mg in strength. Think of it this way... You have a glass of iced tea and it is the perfect strength if you put iced cubes made of water in that glass, when they melt you have diluted it and it is no longer the perfect concentration. Now take that same glass and add ice cubes made of that same iced tea...when they melt you still have the perfect concentration just more of it. Hope that made sense.
Buy the highest nic mg per ml you are comfortable mixing with...Hint...... the higher the better. I started with 100mg per ml and did so in the 3rd week of my vapeing journey. YMMV again I stress safety! Not comfortable with that, start with 50mg per ml.
Menthol
e-liquids are not always just menthol. I make a "smooth menthol"
e-liquid that has menthol, koolada, spearmint and wintergreen in it. DIY section is a great resource for recipes.
READ READ READ in the DIY section of the forum prior to mixing anything....
Get an e-liquid calculator I use the "e-juice me up" calculator that you can find on this forum