Do I really need an 135mm f/2L for portraits?

will 135mm have much better bokeh (around f2 aperture), separation and micro-contrast, separating it from wide-open 85mm, 100mm macro or 200mm, and isn't 135mm too close to these?

I don't have 100/2.8 (neither L IS nor the older version) but to 85/1.8 and 200/2.8 I can compare.

FWIW 135/2 and 200/2.8 feel a lot like twin lenses when it comes to both physical properties (200/2.8 is just ever slightly longer and a bit heavier), in terms of optics both are more than enough sharp wide open.

when it comes to optics 200/2.8 has a bit more microcontrast which helps it for things like sports. and it seems to be more flare resistant which is again great thing for sports. truth being said, when used in Servo on my 6D2 it's the 135/2 that seems to follow subjects better. not sure if you care, but just mentioning it.

bokeh itself is very "fluffy" on 200/2.8 which makes it a dream lens for nature shots. similiar to 85/1.8. the135/2 is a bit less dreamy and perhaps a tad harsher on brighter spots in background. but this is very unscientific impression on my side.

IMHO 135 is different than both 85 and 200. personally, I think it's OOF rendering is less delicate than 200/2.8 (that could also be a matter of just how shallow DOF on 200/2.8 is)  and also 85/1.8 (in this case I think CAs help with softness for f<2.8). whether you need it or not is a matter of personal preferences. I love 135mm focal length and it works like a dream for me. but I can say the same about 85/1.8 (I forgive it the CAs, bokeh of this lens is amazing), just for different shots.