How do seedless vascular plants differ from nonvascular plants?

Great question and it’s one I wish more students would ask. Most people don’t know how plants differ but it’s pretty simple:

Vascular plants (like trees) have tissues to conduct fluids and foods.

Non vascular (like mosses and liverworts) have no tissues and produce no seeds.

Here are some examples:
This is a trillium, found in shaded, moist wooded areas.
Nonvascular are usually small and closely related to their ancestors the alga, They produce spores as their main means of reproduction and usually require wet areas to provide their water needs, nutrients that they absorb, and a means to transport sperm or eggs.

The first is a fern, a seedless vascular plant. It uses spores as well as reproductive cells.
Next image shows comparison of stems.
The final image is of liverworts, a nonvascular type.
Hope this helps. If you get a chance take a class in botany and you will be amazed how cool plants are.