Game engines always convert your mesh to tris when you import them regardless of how you have modeled your project.
In a low poly workflow or game model , tris and n-gons are not an issue , but for a high poly piece , specifically one that will use a subsurface modifier , it is important that you stick to quads since the subsurf mod will not work well with tris or n-gons due to the way it works.
As far as I am aware , any n-gon can be split into tris so you don’t have to worry too much when modelling for games.
Another thing to watch for when modelling are poles (more than 4 edges meeting at a vert) as that can also cause subsurf errors and cause deformation issues on organic models that are rigged to move such as humans and animals.
