I have Wiltshires, Lleyns and woolshedding composites that are some kind of cross - some wilts/lleyn some with other genetics in. I've not been at this size flock long so I'm playing with genetics.
My ewes for fat lamb production go to a SufTex bred to 'do' off grass. I got them from Peter Baber who has a very good reputation.
Wilts do produce a good carcase, but they do tend to finish heavier than the composites, probably as they are big sheep. They can be tricky to turn, they are big and spirited, hence why I am breeding polled easycares - I still run 30 or so pure Wilts ewes though.
All my ewes get nothing but grass (hay if there is snow or they run out the grass and I can't move them) and mineral buckets close to lambing (have had scats bog standard 'sheep' buckets since the snows) - old biddies get a beetlic hi mag as the lambs start to come, but thats as spoiled as they get. All are wormed to FECs every 8 weeks or so (more often for lambs - I fec every 3-4 weeks), last year most grown ewes needed worming twice only. All lamb in April out of doors, all who produce them are expected to raise trips. Anybody that fails to perform goes as soon as is practical. I rarely pull a lamb, I tag etc at birth and then leave them alone. Seems to work for me so far, I struggled a bit last year, but when I speak to other sheep farmers, I seem to have gotten off fairly lightly.
Hope all/some/any of that is helpful.