Gadolhadorah,
“having too many choices offered by the siddur when davening is really hard on my kavanah”
I personally daven for the most part from the Artscroll “Yitzchak Yair” siddur, which I imagine is one of the types you are criticizing. In my experience, the variants in community nusach that are included as parentheticals/gray highlights are much less prevalent than the seasonal variants, e.g., yaalei v’yavo for Rosh Chodesh/Y”T, Al Hanissim for Chanuka/Purim, etc. I can’t imagine that you would want a siddur without these additions, and I’m sure with daily use your eyes can find and follow the flow of the tefilla even when these blocks are skipped. Why is it different or more difficult with the few other additions based on community?