"Irish" pubs in London are now the mainstay of a much older generation, as young Irish don't gravitate to dark, old fashioned places anymore - they don't have the best reputation. Pubs in general are much more airy and light these days whilst traditional Irish ones resemble unvarnished, dark boozers from before the 90s, that's only popular with the older Celtic community -long a mainstay of the working class. These days with Ireland the 'Celtic Tiger' and the richest country in the world that's not a city state, the new set of moneyed, Irish migrants would more likely be hanging out in the wankervilles of the West End, and not be seen dead in a classic boozer.
This of old -almost a trope that Irish pubs all look like this still:
rather than this:
mod versions do a swell remake though (all pictured so far are Irish pubs, as are these)
https://irishpubcompany.com
There's no real difference in English /Irish pubs persay except for the alcohol offered is dominated by Irish brands, usually with Irish memorabilia on the walls and the premises owned independently. Saying that, the most traditional of the Irish boozers are that in name only because of their longstanding clientele and ownership, that will have passed down for generations as a focus for the community - with little overt Irish branding other than being called O'Connors or O'Flynns etc. All-in-all Irish pubs do tend to be more old fashioned.