I often end up with a triangle here and there and always try to fix them the best I can but would it really matter if the Triangle will end up hiden under something like clothing or Hairs etc? Or even better should I just delete those Polygons hiden by cloth to reduce the polygons count?

Although it’s good practice to avoid tri’s if you are applling subdivision smoothing, it’s not the end of the world if you do have the odd one or two here and there if they are in discreet places.

I sometime spend to much time trying to fix a tris or just make my models look worse down the line with too many lines at one spot just to get rid of a tris. =/

Remember that a single Tri will affect any Quads attached to it (when meshsmoothing). If you keep any Tris to a flat area they will have little impact, on rounded areas they will cause problems. Removing a tri poly is a bad idea because it leaves a hole in the mesh and this can affect any smoothing very badly.

Max 4.2 through 2013.
XP-64 (SP2)
NVidia 9800GTX-512 (Driver 266.58).
Core 2 Quad Q6600 2.4GHz, 8Gb Ram, DX9.0c.

I sometime spend to much time trying to fix a tris or just make my models look worse down the line with too many lines at one spot just to get rid of a tris. =/

That really defeats the object of removing tri’s. The idea is to make your model look better. They can cause artifacts or pinching on the mesh, but if they are in an unseen place, or even where it looks right, there is no harm in them. Work on the principle of if it looks right, it is right. So if you have a tri and you apply smoothing and it looks OK, leave it, if it looks bad, do something about it.