I'm running a Shimano 8-speed 12-25 cassette on a bike with a 7-speed group. I just skip the big cog and ride the first seven 12-23 cogs. With a 53/39 chainring and our mostly modest roller terrain it works okay... at least when I'm in shape. I haven't been able to ride much for a few months due to vertigo from a persistent upper respiratory inflammation, but when I rode that bike a couple of times in October it was fine even on the most challenging segments of my usual routes with some short-ish grades that max out at around 8%, but average 2%-3% overall.
I have some SunRace 7-speed cassettes with 11T small cogs, mostly in the 11-28 range. They work fine, but I don't care for the somewhat awkward steps around the middle cogs. Doesn't flow as well as the closer spaced 12-25 cassettes. And I don't like 11T small cogs on any bike. They feel grindy. The chain wrap is too tight for bike chain link lengths. The smallest cog I've tried that turns without feeling grindy and lossy is 12T, but I prefer 13 unless I'm feeling really strong and want to try for a
PR on a couple of time trial segments. (I haven't felt particularly strong this year and at age 64 it ain't getting any better.)
I'd prefer 12-25, 12-28, or 13-25 or 13-28 in both 7 and 8 speeds, but the cassettes and freewheels I want are still in short supply due to the ongoing shipping slowdowns so I'll make do with what I have for now. That 8-speed 12-25 came with an older Mavic wheelset I bought from a guy back in August or September.