>Will this headphone sound mind blowing in comparison to my old closed back ones listening to

Can't guarantee anything, everyone has a different experience with this stuff, at least in my case, i was definitely mind blown, you could not, who knows, although if you say "blow my mind even on the cheapest of headsets." I'm quite positive.

>Really struggling to understand the ease of drivability

Unless you have like a really, really bad source , they should be fine.

>Please bear in mind I am in England so I think the Dongles here are the Undervolted EU ones.

In that case, i would rather look into other Dongles, maybe from tempotec