The internet speed of your plan does not itself determine the actual speed you will get with anything. The other side will have its own speed. The ISP's may throttle various services. The location of the other side will determine speed as well. Even hardware and the hardware's firmware can affect speed eg TCP problems of the firmware can affect TCP connections.
There's a lot of possibilities. To figure it out, you do have to spend time and narrow it down. Martin's comment is only the beginning of that.
There's a lot of possibilities. To figure it out, you do have to spend time and narrow it down. Martin's comment is only the beginning of that.