Container gardening similar to 'fishing' ?

First, I would like to thank the forum members who welcomed me to this forum when I registered as a 'Newbie'
last week.

Next, I want to reiterate my complete lack of knowledge or experience in container gardening or gardening in general.
After spending quite a bit of time going through the various forum posts the last few days I've come to the conclusion gardening is similar to fishing --- everyone has their own favorite equipment, lure, and 'hole'. With this thought in mind, I have a few basic questions I need help with, keeping in mind I am primarily interested in growing tomatoes.

COMMERCIAL POTTING MIX --- Jiffy Mix, Bacto, Promix, Jiffy Pro, etc. --- all similar or some better than others?

COMMERCIAL MIXES --- Use alone or add other mediums?

CAGES --- Is the idea to keep as much of the plant as possible within the cage, or do you allow the vines to spread outside the cage as they continue to grow upwards?

MAGNESIUM --- Calcium nitrate, dolomite lime, hydrated lime, eggshells, 'tums' etc.best? Related question -- can you overdo the calcium?

TOMATO VARIETIES (I'm living in southeastern Pennsylvania)
Room for six containers and thinking of the following --- comments, opinions, and suggestions all welcomed.

2 paste ----- Viva Italia & Super San Marzano
2 cherry ---- Sungold & Supersweet 100
2 slicers ---- Jet Star & Big Beef

These are a few of the basic questions I have at the moment. I'm sure I will have more as I venture forth. ALL input will be looked forward to and gladly accepted!!!!!!!!!