The data is not available for free.
The product is Strava Metro as you said (https://metro.strava.com/), and they sell the data.
You cannot access other peoples tracks through the API without their permission.
You can try the ArcGIS QMS plugin (ArcQMS).
More information see here:
I am not familiar with Strava, but in QGIS you can use a combination of blending modes and draw effects to get a raster-like feel, similar to the image above.
You can find both of them in the Style Properties of your layer (blending modes are under Layer Rendering).
this is how looks like my strava routes, rendered in QGIS. What I do is to merge all gpx tracks (otherwise you should change blending mode one by one) into a single file and then, into the Layer Properties > Symbology tab, choose an appropriate colour, then opening the layer rendering options to select Screen as the blending type for the Features parameter ...
You could get summarised information from Heatmaps https://www.strava.com/heatmap#12.18/172.60535/-43.55162/hot/ride
Or for individual efforts flybys https://labs.strava.com/flyby/viewer/#1556816875?c=rb68pdy3&z=C&t=1QyE0H&a=6yPLXAs0y1xpYctcyeTJXFDzylzmYctcX5J-XQ This shows other strava users who passed near you on an activity, or duplicated ...
I'm not sure where you got this from, but I'm guessing it was from the Glasgow Data Portal? If so afraid there isn't any metdata :(
I found some metadata here, but I don't see that column name in there.
I had a look at the data using QGIS (to join the OSM road network to the strava data on field osm_id). Coloured it using 'graduated', 10 classes, Jenks ...