Only the second option will give you meaningful information. And this one even only if you allow Plex server to perform the “extensive analysis”.
Everything else will only give you the average bandwidth, which can be off by a factor of 3 (and sometimes even more!).
Compare the values of bitrate="5879" and requiredBandwidths="20798,16927,8766,7384,6747,6501,6424,6424"
for the first stream (video) of this MKV file.
<Media id="1231750" duration="7150186" bitrate="11086" width="1920" height="1036" aspectRatio="1.85" audioChannels="7" audioCodec="dca-ma" videoCodec="h264" videoResolution="1080" container="mkv" videoFrameRate="24p" audioProfile="ma" videoProfile="high">
<Part accessible="1" exists="1" id="1234308" key="/library/parts/1234308/1594638307/file.mkv" duration="7150186" file="E:\Animation2\Das wandelnde Schloss (2004)\Das wandelnde Schloss (2004).mkv" size="9899886733" audioProfile="ma" container="mkv" deepAnalysisVersion="4" indexes="sd" requiredBandwidths="26945,23074,14562,13215,12482,11780,11634,11634" videoProfile="high">
<Stream id="2007132" streamType="1" default="1" codec="h264" index="0" bitrate="5879" language="日本語" languageCode="jpn" bitDepth="8" chromaLocation="left" chromaSubsampling="4:2:0" codedHeight="1040" codedWidth="1920" colorPrimaries="bt709" colorRange="tv" colorSpace="bt709" colorTrc="bt709" frameRate="23.976" hasScalingMatrix="0" height="1036" level="40" profile="high" refFrames="4" requiredBandwidths="20798,16927,8766,7384,6747,6501,6424,6424" scanType="progressive" width="1920" displayTitle="1080p (H.264)" extendedDisplayTitle="1080p (H.264)"/>
<Stream id="2007133" streamType="2" default="1" codec="dca" index="1" channels="7" bitrate="2488" language="Deutsch" languageCode="ger" audioChannelLayout="6.1" bitDepth="16" profile="ma" requiredBandwidths="2876,2715,2550,2496,2496,2496,2496,2496" samplingRate="48000" displayTitle="Deutsch (DTS-HD MA 6.1)" extendedDisplayTitle="Deutsch (DTS-HD MA 6.1)"/>
<Stream id="2007134" streamType="2" selected="1" codec="dca" index="2" channels="7" bitrate="2695" language="日本語" languageCode="jpn" audioChannelLayout="6.1" bitDepth="16" profile="ma" requiredBandwidths="3008,2854,2723,2707,2707,2707,2707,2707" samplingRate="48000" displayTitle="日本語 (DTS-HD MA 6.1)" extendedDisplayTitle="日本語 (DTS-HD MA 6.1)"/>
<Stream id="2007135" streamType="3" selected="1" default="1" codec="srt" index="3" bitrate="0" language="Deutsch" languageCode="ger" requiredBandwidths="1,1,1,1,1,1,1,1" title="full" displayTitle="Deutsch (SRT)" extendedDisplayTitle="full (Deutsch SRT)"/>
<Stream id="2007136" streamType="3" codec="pgs" index="4" bitrate="23" language="Deutsch" languageCode="ger" headerCompression="1" requiredBandwidths="50,50,50,50,50,50,50,50" title="full" displayTitle="Deutsch (PGS)" extendedDisplayTitle="full (Deutsch PGS)"/>
<Stream id="2007137" streamType="3" codec="srt" index="5" bitrate="0" language="English" languageCode="eng" requiredBandwidths="1,1,1,1,1,1,1,1" title="full" displayTitle="English (SRT)" extendedDisplayTitle="full (English SRT)"/>
</Part>
</Media>
There is more than one bandwidth value here, because the type of the client determines the practically required bandwidth too. Namely the size of the network receiving buffer memory.
The less RAM is available for this, the more often you can expect to see buffering occur unless there is plenty of bandwidth surplus.
The numbers mean the practically required download bandwidth for 5/10/25/50/75/100/250/500MB network buffer sizes.
(And this is just the video. In the case of Direct Play you must add the bandwidth of all remaining tracks on top, which is what you can see in the requiredBandwidths="26945,23074,14562,13215,12482,11780,11634,11634" for the overall file.)
