Woodwind and String Runs
Runs on strings and woodwinds are a very common effect in orchestral writing and can create very lively textures. However when writing them, put some thought into it. First of all they should always have a motivation and not just be there for no obvious reason. It is best to have runs lead to a target. There are only a few cases where runs work without having a specific target.
Another thing to understand is that runs are effects, not melodic elements. So in order to have them work like a run they need to have a certain speed. Usually 16ths will not really sound like a run but be perceived as a melodic element (unless the tempo is really quick). But also too fast runs can be a problem as they will end up sounding more like a glissando on strings and pretty unclear on woodwinds as well. Considering the notes to pick for the run, most of the time it should be notes of the scale of the current harmony except for moments when these runs lead to a strong hit where you could also use the scale of the target harmony even if it conflicts with the harmony that still sounds during the runs.
Using a combination of several tuplets in order to cover the right distance for your run is also not much of a problem as your musicians will not really count these out but simply play the gesture more or less evenly. 7-tuplets are pretty common as they cover exactly one octave within. Also: use common scales and not awkward combinations of intervals. All musicians practice all common scales regularly and can recreate them from “muscle memory”, if however you use something odd, it will most likely trip them on sight reading and sound “strange”.