I live near Arvada res and manage to fish it a few times a year. I've talked to a few of the rangers, anglers and some of the hardcore "residents" that fish this place continuously.
Walleye...very rare but do exist. The biggest one I have seen here (other than photos) was (2) pounds and about 15-inches approximate in 2002. I think you are correct about the "stocked as fingerlings but consumed quickly".
Muskies...these were more common in 2002 and I have to assume some have been removed. Just like the walleye...rare but do exist. Saw one guy in a boat land and release a beaute muskie in 2003.
Bass...decent smallmouth action with a few over 16-inches. Largemouth are not as good but do still thrive in average numbers with a few good ones over 17-inches. I love the bass so do me a favor and toss these guys back!
Stocked trout...these were much better this year. They stocked it early with 12-inch fish and let them acclimate. This made a huge difference IMO and most of the ones I saw at (weekend opener) looked real fat and healthy.
The key to Arvada res IMO is FISH IT EARLY. "Takers" hammer this water and remove the majority of fish (mostly trout) as the year goes on. Open April to October and the seasonal closure helps maintain some holdover fish population.