I’ve got an ergotron monitor arm that’s got the dual as stacked on a single pole (aka, they’re not attached to each other, on arm is physically on the pole higher than the other) and have been able to use it in a number of config like you want. My current is that the pole is off to the right end of my desk, with my main monitor centered in the desk (arm out stretched) with the second arm (set up to hold a laptop) doubled back on itself in order to hold the laptop off to the right of the main monitor. Let’s me get the correct height on both.

Edit: was looking for mine on amazon and found it. Amazon also told me I bought it in 2011, so it’s worked flawlessly through 3 house moves and I’m happy I made the investment back then. The arms pivot up and down and don’t need both sections which makes it much more versatile than other mounts suggested.

Ergotron - LX Dual Stacking Arm - 25-Inch Extension, Polished Aluminum https://www.amazon.com/dp/B0036RDOT8/ref=cm_sw_r_cp_api_i_EVT9DbJCRD863