I would not boil the tanks. There are several rubber grommets that might get compromised and start leaking or even shorting out the power.
I use distilled water. Soak them for a while, swishing then every so often. Change out the water and repeat. You could also try the vodka.
I do not use denture tablets for tanks, tips, condoms. Only use for me is the coil head, if I neglect it and it gets too gunky.
With the exception of a few strong flavors (like Tiki), a distilled water rinse soak is more than sufficient. I do try to dedicate tanks to flavor families, one for mints/menthols, one for fruity, and one for chocolates. I like to keep these tastes separate.