I presume you mean an sf::RenderTexture that you can draw to. This allows you to draw to it and then use it as a texture, then allowing you to draw that texture (such as on each separate window perhaps). However, drawing that texture would still require a draw call but it would be potentially fewer vertices (only need 6 vertices for 1 quad/2 triangles).
If it's very many vertices, it may be worthwhile to render to a texture and then duplicating from the texture but there is some (significant) overhead with a render texture so if drawing the vertices separately doesn't cause any issues, you could consider keeping with that.
In addition, if you are making many draw calls then drawing to a render texture can reduce the number of duplicated draw calls. However, it might be first better to consider ways to reduce draw calls on the original output. If there are a lot already, maybe this is already too many.