Some people pinch and prune tomatoes. I've never found that to be any particular benefit. You may get larger tomatoes by pinching, but you won't get as many tomatoes, and more importantly, by pinching early blooms you won't get as many EARLY tomatoes.
I grow both strawberries and bell peppers in containers and both do well. A single strawberry plant could do o.k. in a one gallon container, I put eight plants in a rectangular container that is approximately one foot tall and 12 inches wide by 24 inches long. For me a bell pepper does best in about a three gallon container, which is called a five gallon container by the nursery trade standards. Black nursery pots have a weird standard where a one gallon is really just a bit over a half gallon and a five gallon may be as small as about three gallons actual. I think the very smallest sized container for an indeterminate tomato would be perhaps 14-16 diameter and 16 inches deep. Tomatoes are heavy feeders, and also go through a lot of water in a day. During hot weather, a fairly large pot may still have to be watered twice per day, and the plant may still suffer from irregular water availability. IMO container tomatoes really should have some steady supply of water like with drip irrigation on a timer.
For me basil, thyme, oregano, cilantro, parsley, rosemary all grow well in containers. Many other do as well, but I don't have experience with them. Any of the mints are perhaps best suited for containers, as they tend to be so invasive when placed in the ground.
I wouldn't worry about taking a cutting of the rosemary and using rooting hormone on it. After all, the plant that you bought was probably started that way, with them using rooting hormone. If I were you, would buy me another plant or two, whatever is needed to supply your needs. We have a large rosemary bush planted in the yard and snip from it, which is an endless supply, being about three feet tall by three feet wide.
By the way, a true five gallon bucket is somewhere in the neighborhood of 12 inch diameter and 15 inch height.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.