There is useful information from the RNLI here:
https://rnli.org/safety/lifejacketsI have worked in the Search & Rescue world for just on 25 years and I have extensively tested (in controlled conditions
) lots of different lifejackets and PFDs to see what 'works' for anglers.
The thing to remember between a basic floatation device (a buoyancy aid) versus a lifejacket for adults is that lifejackets over 150 newtons are designed to help support the wearers airway by being theoretically capable of turning an unconscious person on to their back - but this is only half the story. Anglers are often encumbered by heavy clothing, waders and gear that they'd rather not let go of (like that nice Winston rod and Orvis reel - other brands are available) which can cause issues....
Tackle can be replaced, a life cannot.
I'd look at 150N as being the minimum. 275N is maybe a bit much - they are primarily for offshore use - but the chunkier you are, or if you regularly use float tubes or spend time afloat then lifejackets can be had in various sizes which will support an angler wearing more gear. I use an older 175N where I need to wear one, but will probably replace that with a 190N Crewsaver in the near future.
In all cases make sure the jacket has crotch straps and
use them. In testing we found this was the biggest single difference in how lifejackets performed. If you're worried about wear of the straps on the Simms breathable waders you're wearing, pop a protective sleeve over the straps.
Most importantly - try one on if you can, before buying. It needs to be a good fit.
H