Splitting data across measurements or introducing tags

After spending some time thinking about the schema design and reading about recommendations out there, I have understood that it is preferable to:

  1. Avoid writing excessive metadata as tags every time a new data entry comes in. E.g. if I have a sensor measuring pressure, it might not be a good idea to insert the unit ( Pa ) every time I insert a new pressure measurement to the database, but rather store the unit in a separate database or a separate bucket.
  2. Avoid splitting fields across measurements if there is a need for comparing or performing math across fields

I am not quite sure, however, how one should balance between these two recommendations. My use case is that I have IOT-devices that produce up to several thousands of time series. The internal structure of the data coming from the IOT-device is:


where a specific tagName may have one or several subcategories (in this example case measurementValue, lowLimit and highLimit) that produce the actual time series. At the time when the data is inserted into influx it is not known to what extent the time series from the IOT-device (also across tagNames) needs to be compared internally or to what extent math operations will have to be done across the time series.

Would it make more sense to organize the data according to Option A:

measurement: IOT-device
    field key: tagName1
        tag set: type = measurementValue/lowLimit/highLimit
    field key: tagName2

Option B:

measurement: IOT-device
    field key: tagName1_measurementValue
    field key: tagName1_lowLimit
    field key: tagName1_highLimit
    field key: tagName2_measurementValue

or Option C:

measurement: tagName1
    field key: measurementValue
    field key: lowLimit
    field key: highLimit
measurement: tagName2

Spontaneously Option B sounds least appealing but does someone have any good guidelines on how to balance between the above mentioned recommendations and what the implications may be in this case when it comes to choosing between option A, B, C and possibly some options not thought of yet?