Seems to me that types and techniques of using ground tackle are pretty geographic-specific. My first boat was a Catalina 30 on the Columbia River (Portland, Ore). In that area a 20-22 lb Danforth on 1/2" nylon and 20'' of 5/16" chain worked perfectly. The bottom was usually muddy and there was usually not much wind, just current.
After a summer on the river we took the boat to southeast Alaska. Had frequent problems dragging even with 6/1 & 7/1 scope. The bottoms here are frequently mud & sand, but often rocky, often grass or weed. The anchorages are often windy.
Bought a 35 lb CQR and noted a great improvement, but still dragged occasionally.
Bought a second 35 lb CQR, put 50'' of chain on it & got in the habit of using both, set separately with a roughly 45-90 deg angle between them, both from the bow. No more dragging.
My present boat is a 33'' 7 1/2 ton (long tons) cutter. The bower is a 45 lb CQR on 35 fathoms of 5/16" chain. It does not drag, period. Usually anchor on 4/1 scope, sometimes a lot more. The most secure anchoring situation here is an anchor off the stern and a tree line ashore, where the situation permits. My second anchor is a 22 lb Danforth that is rarely used.
My point being, different anchors work in different places.
On the side, the frequently published recommended anchors weights for sizes of boats are not very helpful here. Increase size by two over the recommedation, & you''ll probably be OK. And lots of chain, or all chain, works great. My ground tackle can be hauled by hand, but not fun. The Simpson-Lawrence No. 555 manual windlass is nice, when it''s not broke down.
I''ve seen bent Danforths & Deltas. Never seen a bent CQR.
5/16" chain on a 7 1/2 ton boat seems a bit light to me, but the chain has been well tested, being 25 years old and experienced, but shows no sign of stretch.