Just depends. On the fish, mainly.

Walleye I usually vacuum pack. Same with Steelhead. Because you can put a nice long fat piece of fish flat into the bag and suck the air out. Catfish too, if I decide to keep some.

For smaller fish- perch, bluegill, and crappie- I usually freeze those on a tray with wax paper, then either put them in a vacuum bag or just ignore the tray and freeze in water. First, because they don't lie as flat in the bag and it leads to a lumpy vacuum seal that curls them up sometimes, and I usually pan fry my fish. Meaning flat is good. Second, because it's easy to freeze one meal in a vacuum bag with bigger fish (one fillet for a big fish, 2-3 for smaller eyes) for one person, but perch is more like shrimp. Freeze a pile of 'em and grab a handful. I just find that easier.

Main thing is to keep the freezer burn off of them if you plan on keeping them long term. Any fish I plan to eat within a month I just toss in a bag, burp the air out of, and freeze it.