This is a process that has been ongoing for me since at least around 2010.
I do know for a fact that always blocking ads & then running Brave for around 3 years has blocked a LOT of data collection from the simple fact that I never really get any tailored ads. The only exception is airlines really.
My Qube number 1 will be for open and official data. Will keep my old Gmail account along with banking and government contact there, probably even without a VPN.
Number 2 will be for cryptos and all sorts of services that are a bit more sensitive. As a lot of this comes with KYC and such it will still be “official” but with a VPN or sometimes using sys-whonix instead I guess.
Number 3 is then based on data that should have NO connection to the others. In other words this one is where I build another online presence from scratch. (Not talking about any illegal or black hat antics here, merely NOT giving any real data)
This is where I’ll do anything from reading & posting on forums that belong to this level of sensitivity, keep some of my privacy coins and in general feel pretty secure that there will be no direct links to Qube 1 & 2 that could lead to ALL of the (scarce) data from this Qube being spliced or connected with the others.
Number 4 remains to be decided upon, but if I build that it will be done via number 3. I do not have any real need for doing this, but if the need arise I will be prepared. Mainly talking about IF there is some very serious situation like a civil war here, I’m living in South East Asia after all. Could even happen that there is some push to “get” foreigners, and I might have to get info, contact helpers or whatever worst case.
Number 5 is for personal writing and files, so that is simple - NO networking for this one! 
Now, I do fully know that all of this is NOT watertight in case someone targets me, But all I want to achieve is to know that I’m not feeding the digital beast more than I really have to, and that I’m also feeding it totally false data when possible & legal.
I’ve done this consistently since I first got online in 95 or so, it simply makes me less stressed
Possible problems could be:
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Real MAC address leaking, Will keep it randomised, and never use at least 1 of the Qubes without a VPN. 1 will also always be using Tor
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Some activity might get fingerprinted from browsers. Qube 1 & 2 will be using Brave, possibly with two different logged in accounts. Number 3 will be using the Anon distro.
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Being sloppy & logging in to services across Qubes. This is definitely the gotcha… Which is why I will put quite some effort into sorting things out, splitting services up & deleting data as well. Getting the right habits is the main thing anyway, its just great to be able to do it in one OS!
I’ll also get onto analysing my own traffic while online too, its been ages since I’ve done that apart from defending a NAS against Chinese bots and so on
Looking forward to getting far better CONTROL again!