Yes. Peppermint tea grades A on fodmaps, fructans, GOS, excess fructose and polyols, and it is one of the herbal infusions routinely allowed through the elimination phase of a low FODMAP protocol. The usual trap is a blended tea rather than a pure peppermint one, since chamomile and chicory heavy blends behave very differently.

No, and it is worth being clear about the gap. The clinical evidence for peppermint in IBS comes from enteric coated oil capsules delivering a concentrated menthol dose past the stomach and into the intestine. Steeped leaves release a small fraction of that, and much of it acts in the stomach instead. Peppermint tea is a mild carminative that many people find soothing after meals, which is a reasonable thing to expect from it, but it is not the same intervention.

For some people yes. Peppermint lowers pressure at the lower oesophageal sphincter, so it can make reflux easier, and mint is commonly named in reflux diet advice for exactly that reason. The volume matters too: a large hot mug shortly before bed is a worse setup than a small cup mid afternoon. If you have GERD and drink it nightly, it is worth two weeks of logging before deciding it is neutral.

None. It grades A for caffeine because it is an infusion of Mentha piperita leaves rather than Camellia sinensis, the plant behind black, green and white tea. That is what makes it useful late in the day for people tracking caffeine driven insomnia, reflux or palpitations, and unlike decaffeinated black tea there is no residual trace to account for.