Recording Controls Output Format, "FIT and GPX"

no you missunderstood

you can not have fit file with much  more data then the associated gpx file. Those files have to contain same information. As gpx can not be unlimited, the fit has to be limited in this particular case.

Do not expect common support to have acces to all details. This hardware might have been on the market for some time, but when you would compare the functionality of today and one year ago, you will not recognize the device at all. Some versions of the firmware were really dangerous, some did drain the battery in few hours.

Even professional support has not acces to all detail, many things are simply not disclosed to end users.

Sometimes to have someone with close contacts to devs might be useful.

My understanding is that the FIT file is binary and that the GPX file is ASCII. 

Binary is stored more efficiently than ASCII. So a FIT file will be a smaller size than a GPX storing comparable data..

In addition, I think the Explore website has more storage limitations than the Connect website. Documentation for Explore says it is limited to 10,000 points per track. I don't know if they've modified this or that limit still exists.  I couldn't find any documentation for Connect, just some comments in forum that storage is very vast.

If Support is wrong, I'll let them know.  But I'll have the facts later today.

exactly, so the size of the fit has to be adjusted to the capability of gpx, as the data content needs to be the same defined by the max data content of the gpx

Support can not have all details. abt 4 years ago, I was asked by the support to do lot of tests for them, as they could not get some answers from the devs.

I don't understand why fit has to be adjusted. When gpx track reaches maximum, start a new gpx track.

Like2Hike said:

we should all be wary of atlas_cache.

As you wish!

Like2Hike said:

I really thought that when I started this thread, being that the device has been out for a couple of years, I would have a rapid answer from someone and I could move on. Surprise!

You are choosing to ignore the answers that have been provided. 

Your answers have zero explanatory value.

All you get from support is the opinion of the person with whom you are communicating. The responses to theoretical questions like this are notoriously variable.

Yes, .fit is binary. Yes, .gpx is text (not necessarily 8-bit ASCII, but text). The .fit file contains different information than the .gpx (for example, fitness info like heart rate if recorded with appropriate sensors). I doubt that comparable track points could possible be larger than the .gpx. 

Trying to back into the relationship between file size and "number of points" limits is just speculation. Lots of theories will fit the facts. One of them might even be correct. Or not. But I don't know how you would tell when you got the right one.

Note that the limitations associated with explore.garmin.com, or connect, or the mobile apps, or whatever are probably arbitrary. Some programmer somewhere threw darts and picked numbers. The only one I know of which has SOME rationale is the one that limits routes to 200 points. Even for that one, there is no real rationale for that particular number. But at least it's used consistently :-D

Agree with what you wrote, but the only question is, is the Activity file limited or not?

Everything is limited, if by nothing else, storage space.