Hello there Z3u$,
If I understand correctly you are seeing your browser history across all the devices you have updated to El Capitan. This indicates to me that iCloud has Safari enabled in your System Preferences according to the Safari Help site:
Search your browsing history
https://help.apple.com/safari/mac/9.0/index.html?localePath=en.lproj#/ibrw1114
Safari uses iCloud to keep your browsing history the same on all your Mac computers and iOS devices that have Safari turned on in iCloud preferences.
You can stay signed into iCloud but you would need to disable Safari in your System Preferences to stop this happening:
Change iCloud feature settings
http://help.apple.com/machelp/mac/10.11/#/mh80b67854f2
Use iCloud Preferences to change iCloud feature settings. To open iCloud preferences, choose Apple menu > System Preferences, then click iCloud.
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