Anything you can suggest for evergreen with lollipop shape of 2 m bare trunk at the bottom and 4 -6 m max mature height in full sun, clay soil, rather dry. Probably one of the pines fits this description, but I am having troubles finding one with limited height and 4 m width as well. One of yews could be shaped like this, but it could be 20 year project and I want something sooner. For Toronto area.
Thank you for contacting Toronto Master Gardeners with your interesting and challenging question.
A possible candidate for your topiary is Eastern White Cedar Thuja occidentalis. It is available in the usual green, some varieties of which remain a good green over winter, while other varieties have a golden tone to their foliage. Regular trimming of the lollipop shape would ensure that it fills out well and increases the density of the foliage. Cedar is not particularly demanding but would require watering regularly, and a mulch of compost will help to keep the root zone cooler and moister while also supplying nutrients.
As you suggest, a Pine tree would also provide evergreen topiary and suit your sun and soil conditions. There are also some boxwoods that are trimmed into balls of one, two or three that could be quite nice
We wish you every success with your topiary project.