You can use MEW with Firefox/Chrome etc in a safety workplace qube and ordinary web surf side by side. Keyloggers malwares and other harmful stuff never reaches your safety qube.
Long term Qubes user here.
This isn't universally true. Qubes certainly provides a different standard of sandboxing, but is not necessarily absolute security. You need to use a CPU with virtualisation instructions (especially IOMMU instructions) to get the highest standard of compartmentalisation, but even Qubes has had it's critical bugs over the years (although to be fair, the serious problems were upstream issues with the Xen hypervisor, not with Qubes itself).
So it pays to be aware that Qubes still depends on the integrity of it's hypervisor for it's security. However good that is, it's not infallible. Make your decisions (especially concerning your BTC) with that in mind. e.g. I still use a separate offline machine for my private keys, I consider Qubes and an offline tx signing machine to be a complete system, not just Qubes on it's own.
Really appreciated with your constructive comment. Hope to see Qubes OS will over come that all issues. For now, I'm gonna go same way with you, an offline machine side of my operational one. Cheaper than loosing my funds
Addition to general safe precautions we should use our PC's as safely. That topic is far away than cold storing.
If you need maximum anonymity and security, then use OS Tails on your USB storage and "Linken Sphere" browser
For anonymity Tail OS is awesome but for safety I'm not sure as well. Tried it several times however for daily use Tails some boring
. I do not mention all details here you may look up docs of it and Google. I think you gonna like it just like me by the time of progress. I want to see other experienced users who already used or still using Qubes OS what under that topic comments. Please share with us your thoughts.