Yes Redwood standard is good but the larger size of the 14x12 is better as the greater volume allows for more mackerel but they can be heavy to move and may require two people. It could be said that for mackerel you need the 14x12 as they are prolific and big colonies. I like the mackerel as its UK reared.
I have a 14 x 12 I'm using without the runners so that it is top space, first winter though so jury is still out. I put a little vaseline where the frames run and it works well. The brood box sits on a standard wooden floor and takes either its own supers or cedar ones. I put in the inspection trays to check the drop today and had a quick look in the top. The bees are not clustered. The ordinary roof seems OK without any extra insulation.
It looks neat, neater than the Paynes box and much better than my MB boxes which are now sans lip.
It's easier to pick up than the Paynes box too.
Mine are standard, can't see performance being affected by dimension though, I'd imagine similar, favourable reports.
Only thing I'd say, that applies to both is they are TBS. The runners convert the hive to BBS but a lack of recess in the bottom of the boxes means you crush your bees if you go this route.
Chuck the runners and go TBS. Nice hives.