That's a great chart you show.
You can see in the three lines for 2 toroids, that more turns help the low end, but too many turns hurt the high end of the band. This is because of the inter-winding capacitance, and especially the capacitance between the first and last turn which tends to short-circuit the toroid. (I think there's a rule of thumb about winding only about 270 degrees around the toroid).
With thinner cable you can certainly put on more turns without suffering the same problem, but I guess there's still some benefit to spacing them out slightly. So perhaps aim for 12-14 turns?
There's no issue with the cable being close to the toroid - it's not electrically conductive. Rather keep it tight for mechanical stability and to keep the centre-passing wires as far away from each other as possible.
4:1 baluns have a phasing issue with too many turns, where one path through the device is delayed compared to the other, which limits its high frequency performance. This isnt' a problem on a 1:1 balun, so the cable can be as long as it needs to be for optimal winding performance.
Be careful about the power handling if you're planning to use a mismatched antenna and an antenna tuner. RG-174 should be OK for several hundred watts at HF, but only at 1:1 SWR. If it's 2:1 the power handling will drop slightly, and for high SWR like 10:1 or more, it will be much less, maybe one quarter, I can't remember the formula.
Finally, don't worry too much about the bend radius of the cable - if you abuse it once, gently, you may affect its impedance but that won't matter much in this application.