Though Ralph Lauren does not have extended sizes, in terms of length, I can speak with authority that the Polo and Double RL lines tend to fit longer than most standard lines. In particular, I am a fan of the dresses and sweaters. They do not just fit; they flatter.
Since mid-quarantine, I started stocking up on Polo Ralph Lauren dresses. I truly feel that they are designed with the tall girl in mind. This is for two reasons: not only do all of the hemlines of the dresses I procured hit at a flattering spot on the leg, but the cut and length of the dress torso are fit as well. As a bonus, the sleeves are long enough on the only Ralph Lauren long sleeve dress out of my RL collection; this almost never happens for standard length clothing lines.
Ralph Lauren makes the most fantastic sweaters. Fair isle, cable knit, cashmere, tennis, or southwest-inspired, the brand nails them all. Again, like the dresses, the best part of the sweaters is the fit. The length works on both a long torso and long arms.