I see these as very different. Te is about abstract knowledge - assessing externally defined knowledge, organizing, demonstrable proof, evidence, theories. Disciplines like law, accounting, engineering, medicine, etc. have strong Te components. It's different from the internalized Ti which is more about logic, and tends towards both more originality and distortions since it isn't as beholden to external systems. Te is judging reality from externally verified systems of thought proven through evidence and reason.
Se is perception of the external concrete world as it is. It has to do with seeing details and being able to respond. It's knowing oneself in the context of the sensory world. It is the opposite of the person lost in thought, spacing out, but instead about being present, conscious, and aware of the world around through the senses. It is neither rational or irrational, but more just awareness.
When Se is combined with a judging function it can make a person skilled at navigating in a quick, improvisatory manner. Activities that require quick responses like racecar driving, firefighting, boxing, heart surgery, sports, etc. can be done well with changing, unexpected, new scenarios when using Se combined with Te or Ti. When combined with Fi or Fe it can be a strength for improvisatory creative expression in the arts or dance for example.
Si has more internalized constructs of reality, so can relate best when the outside world matches the internal constructs - goes according to plan. Si is better at mapping details and recreating them. Se can respond to new sensory situations more quickly having few internalizes expectations.