I'm a veggie and use quorn a lot, it suits me fine and doesn't do to much damage to my BG. BUT I mainly use the chicken pieces, sausages, mince and bacon. I occasionlly ahve the burgers or lamb grills but they are higher carb.
I don't eat the fillet with breadcrumbs etc as they are quite carbiferous, as are the ready meals, because they usually have rice or potatoes or something in them as well.
If you are cooking something tasty the the pieces and mince are quite a good as they take up flavour but they don't need much cooking at all. I make spagetti bolognese, chile, a 'lasagne' using slices of celeriac, hotpots again using celeriac, curry. I make a cheese sauce with cream and melted cheese and pour it over quorn and caulifower, for a caulifower cheese.
But quorn does ocntain carbs so if you are counting carefully don't forget to include it in your totals.