Regarding this triangle
If I really needed something all quads would this work?
If it is an absolute must, yes! this would work.
In the lesson, I think Jonathan says this is one place it would be ok to use a triangle.
And he also talks about keeping it as simple as possible, adding extra geometry unnecessarily.
Is there a reason you wanted to make it all quads?
It would work, but look at the edgeflow that would create:
If you'd want to creat edgeloops there, they would go through areas of the Mesh where you don't want them (probably).
Yes he does refer that it is ok, althought the only reason its because I hear all the time in most videos across multiple platforms "try to have all quads in your mesh!", I really thought that in order to have a perfect mesh everything should be all quads
And when I saw this triangle it gave me a little bit of confusion since I am a new user and I still have many questions regarding meshes of quads and triangles... but is there a video lesson about that in another course?
Yeah it seams about right so if I inset that region I could lock the edge flow?
Well, the original triangle stops the edgeloops from going all over the place.
I am not sure what region you would like to Inset, but in general that wouldn't 'lock' the edge flow.
And as a sidenote: if Jonathan Williamson says it's ok to use a triangle here, you can be sure that it is absolutely fine.
It would be this region to "lock"
Well i do trust that this triangle works, its just... this situation lets my mind running like crazy thinking about this and trying to understand why and when I should use the triangles is there any lesson to view or review to better understand this kind of subject? Or is it just one of those things that comes with practice?
Triangles will upset your face loops, as will N-gons, if for example you want to add a loop cut.
The use of triangles will come with experience, but they are not all bad if used correctly.
Insetting that area doesn't get rid of the triangle:
But the thing with all quads is important with subdivision surface modelling and there you can use triangles sometimes.
Simply said; a Triangle stops an Edgeloop and a Pole ( a Vertex with more or less than 4 Edges connected to it) re-directs an Edgeloop.
Do look into the 'Fundamentals of Modeling' course by @jlampel .