Yorkshire pudding - how do the proportions of the ingredient affect shape, texture and taste? Some very interesting posts, like this one, which has links to some more extensive discussions and websites that I consulted, too, describe some aspects of the method used to prepare and bake the batter, affecting the end result.

However, a sentence in one post:


  You can play with the ratio of ingredients every which way and still end up with a batter that rises tall.


left me quite baffled, because I thought: surely the composition of the batter must matter to some extent...

From a little research on the topic, I found that, indeed, the proportions of the ingredients vary widely between different recipes, but I could not find any extensive account of how that impacts the outcome.

See below the links to each recipe I looked at, and the % of ingredients, in order of egg to flour ratio.

Allegra McEvedy
Egg = 19%, Flour = 24%, Milk = 57%, Water = 0%, Egg/Flour = 0.80

Tom Kerridge
Egg = 26%, Flour = 29%, Milk = 45%, Water = 0%, Egg/Flour = 0.89

BBC food
Egg = 22%, Flour = 22%, Milk = 44%, Water = 11%, Egg/Flour = 1.00

Serious Eats
Egg = 36%, Flour = 27%, Milk = 32%, Water = 5%, Egg/Flour = 1.33

Mary Berry
Egg = 31%, Flour = 21%, Milk = 47%, Water = 0%, Egg/Flour = 1.50

James Martin
Egg = 33%, Flour = 18%, Milk = 49%, Water = 0%, Egg/Flour = 1.78

However you look at it, Egg/Flour ratio, (Egg+Flour)/(Milk+Water) ratio, there is a huge variability.

I experimented a bit, although I did not make all of them.
Allegra McEvedy's version is my favourite so far, whereas other recipes (I won't say which ones) gave me stodgy, undercooked puddings, a completely different thing, despite the fact that the method was to all practical purposes the same.  

Q As per title of this post, would anyone be able to please point me to posts or websites describing how the batter composition affects the end result, e.g. in terms of shape, texture and taste?
I take it you didn't read Kenji's Serious Eats column The Science of the Best Yorkshire Puddings which is linked from the recipe column.

It discusses his experiments with various factors affecting Yorkshire puddings addressing some of your points including liquid (eggs + milk + water) to flour ratios and amounts of fats (yolks + milk) as well as technique.  The focus is on balancing expansion, crispness, and the hollow with some mention of richness (fats).

[EDIT]

Major points:


Let rest overnight ("Resting your batter is the single most important step you can take to improving Yorkshire pudding and popovers.");
Starting with colder batter gives denser, more cup shaped; warmer batter gives taller, crispier with a hollow core;
Water added to milk gives a crisper pudding (not needed for skim/1% milk);
Hydration at least 200% and no more than 300% (266% in his recipe) - higher hydration gives "a pudding shaped cracker", lower gives deeper cupping;
Pre-heating muffin/popover tins not required, but essential for cast iron pans;
You can open the oven without ruining it;
Beef drippings are best.