Often, but not always, a title given to and associated with God will be written as two words in Hebrew. They might separate the words with a makkeph, which looks like a dash but is at the top of the line instead of the middle (technically, this makes the words one in Hebrew and shifts the accent).
If there is no makkeph, the words will be written as two words, El Roi.
In personal names, the name will translate in a way that shows this person is not to be confused with God. For example, Daniel means "El is my judge" and Michael means "Who is like God?" In the second, we know this is a question and not a description of the person (saying the angel is like God) because Hebrew grammar says the Mi prefix (and that's a long I sound) at the start of a clause is the question "who." To say "X, who is like Y" would use the relative pronoun asher.
Regarding El Gibbor in Isaiah 9:6, the same name is used in Isaiah 10:21.
A remnant will come back, a remnant of Jacob, to the mighty God. [NET Bible]
This verse stands in parallel to the last half of 20:
Instead they will truly rely on the Lord, the Holy One of Israel.
The Holy One of Israel refers to YHWH. Therefore, El Gibbor would be referring to God in 10:21. I would interpret El Gibbor in 9:6 the same way.