Yes, you can put a carto tank onto the E-Power 14650 with no problem. The Smoktech 3.5ml tanks are a very nice looking match.
You can't use the E-Power 14650 cone with a tank. Just leave the cone off. There will be a gap between the bottom of the tank and switch leaving the cone threads exposed. Looks OK to me, but some people get fuzzy about cosmetics and don't like this look. Some have purchased a cone as a replacement part and cut them down to fit between the switch and tank.
You can't use the E-Power 14650 cone with a tank. Just leave the cone off. There will be a gap between the bottom of the tank and switch leaving the cone threads exposed. Looks OK to me, but some people get fuzzy about cosmetics and don't like this look. Some have purchased a cone as a replacement part and cut them down to fit between the switch and tank.