Hi,
The playback method will vary depending on your delivery profile.
If you are playing with HDS and HLS, which support adaptive bitrates, like you said, the flavour served will change based on the user's network conditions.
If you check KMC->Content->click on entry name->left pane, flavors, you will see that each entry has several copies of the entry, with different format, bitrate, dimensions, etc.
Note that not all source entries can be converted to all defined flavours, since some sources may not be of a high enough quality.
You can control the desired flavours by going to KMC->Settings->Transcoding settings