I avoided corset tops for years because the ones I tried on in my twenties dug in under the arms and made sitting down feel like a negotiation. What changed was trying a properly boned one in a shop changing room on a slow Tuesday, with nowhere to be, and realising the bad fit had never been the idea, it was just the version I kept buying.
Honest limits first, because there are plenty. A corset top is the wrong call for anything that involves bending, reaching, or a full day on your feet, so school runs, office days with a lot of stairs, or a long train journey are all off. It's also not forgiving after a big meal, the structure that holds you in doesn't give the way a jersey top would, and I've regretted wearing one to anything with a buffet. Summer is really its season, worn alone with the heat doing half the work, or layered under a blazer in fairly mild weather. In proper cold it's miserable, there's no room for anything warm underneath and the fabric itself rarely has any insulation to speak of.
What separates a decent one from a disappointing one comes down to the boning and the fabric doing their jobs together. Cheap versions use thin plastic boning that warps after a few washes and starts poking through at the top, you can usually feel it if you run a finger along the seam before buying. A better one has boning that holds its shape without feeling like scaffolding, proper structured panels rather than just a shaped seam with elastic behind it, and a lining that doesn't go see through the second you catch the light. Hardware matters too, the hook and eye or lacing should sit flat against your back rather than straining, and if it's already gaping on the hanger it'll gape worse on you by evening.
Fit is where most people, me included, get it wrong twice before getting it right. Go by your ribcage measurement rather than your usual top size, because a corset top that's a size too big won't adjust down the way a normal top would, it'll just sit loose at the bust and dig at the waist, which is the worst of both. Try sitting down in the changing room, not just standing in front of the mirror, because that's when a badly cut one reveals itself, digging under the bust or riding up at the back. A good one stays put.
Next time you're looking at one, check the boning first, press it through the fabric and see if it moves or flexes properly, that tells you more than anything on the label.