Several years back I built some Lasagna Beds, which basically are multiple layers of greens and browns. They have the benefit of being able to plant in them immediately, which is different from Inter-Bay Mulch which ages under a covering for some months before you plant in it.

Making Lasagna Beds is like ringing the dinner bell for worms. Within days, if not hours, of their creation worms are working their way into the mounds and eating the greens. Within a week to ten days they are super-loaded with worm castings and as such are extremely fertile.

I was somewhat of a novice to growing tomatoes then and planted one of these lasagna beds with a three or four Yellow Pear plants. Yellow Pear in any soil is going to be a huge plant and a heavy cropper. Yellow Pear in the super-rich soil of a lasagna bed is a plant with insane motives to take over the world starting with your own garden. I did not notice a decrease in fruits, certainly who could tell with any cherry as most are mega-croppers anyway, but the immensity of the plants was astounding. They were so enormous I pruned them with electric hedge clippers ;-0 They were unfazed and in a few days were just as big as before I had pruned them. They cropped like mad and because there were so many fruits I couldn't clean them all up at the end of season and then they reseeded like mad the following year. It was an invasion of Yellow Pear tomatoes. I like them, I do think they're quite refreshing and sweet to snack on as I work in the garden, but I don't like them by the thousands.

Worm castings do indeed contain nitrogen--all poo does, lol. It is gentle and generally doesn't burn roots, and it is a good fertilizer for plants--you can even make a diluted fertilizer tea with worm castings which is marvelous for container plants. There's nothing wrong with using fertilizers on tomato plants, but using too much fertilizer can give you large plants with disproportionately fewer tomatoes. A fertilizer with specific numerations meant for tomatoes is always a good choice if you follow the directions on the package and don't over feed your plants.

Of course, you can experiment to see with your own eyes how this works and with similar plants in their own containers or beds give different fertilizer treatments--see how it works out for you and learn from the experience to tweak your methods.

In my own garden I try to keep it simple. I dig in grass clippings each spring before planting and in the fall I rework the beds and turn in fallen leaves. When I transplant my seedlings I wait a few days and side dress with a slow-release granular fertilizer for veggies and/or tomatoes, I can add more fertilizer a few months later but I usually don't bother. The garden grows fine as it is.

I think the best thing you can do is just figure out what would be easier for you to do; what are your priorities with the amount of care, effort and time you want to put into growing a few tomato plants. Reduce your concerns by eliminating what you no longer trust and go with what you know works for you.

My experience with worm castings parallels yours; incredibly bushy, huge, riotously healthy looking plants and just the plants with it. I'm gonna try tomatoes this season with just dolomite lime, kelp, maybe a tad less worm poo and nothing else. Enough is enough (;-)