None of your water choices have the quality you want for carnivores. There's no harm in using the spring water for most orchids though, but it is likely that your well water and the spring water are pretty similar, so you might save yourself the trouble of collecting and hauling it, unless testing shows the well water to be significantly harder and more alkaline (higher pH).
200 ppm GH is moderately hard, but if you repot annually it probably isn't high enough to be a problem in most cases. pH 7.3 is a bit higher than optimal for most orchids, but if you are using a water soluble fertilizer and organic medium (bark, moss, etc.) they probably keep the pH somewhat below 7 where it should be.
40 ppm nitrates is just providing a little nitrogen in exactly the form many fertlizers do. Probably not enough to suggest any changes in your fertlizer use though.
To find any kind of relationship between hardness and TDS you have to make the assumption that almost all of the dissolved solids are calcium and magnesium carbonates. That's a very large and inaccurate assumption in some places, and proibably not worth the effort for a very rough approximation that might be seriously misleading.
Softened water is usually the worst choice for watering plants - you generally just replace the calcium and magnesium ions (which plants need) with twice as many sodium ions (which plants do not need.
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