Beware when shopping for mattresses, store clerks will try to get you to commit by telling you false information. These 120-day return policies are a lie (unless it's Costco), of course they can deliver to your place in no time, there's no peak season, no. you don't sleep better in X and you don't need Y. They use all the sales tactic they can find (for example, if you're a couple they'll try to figure out who is the more opiniated of the two and side with them to force a buy).
In addition, all these brands are all owned by the same people. Tempur pedic, sealy, stearns, etc. There is no "luxury mattress". Past a certain price point (which I suspect is ~$500) it's all wasted money.
Don't trust the reviews! Nobody buys a mattress, sleep on it for a year or two, and then leaves a review on Reddit or on another website. It's all fake reviews. Any review that tells you X is bad, Y is much better, is basically fake. Don't trust what you read on reddit.
So what should you do? Costco or IKEA, that's it. Both have