I'm currently powering LG's 49" Ultrawide (5120x1440).
One thing to keep in mind is that you
will be running hotter because of the external monitor being connected (i.e. temperatures will start to peak faster, and you're likely to run into thermal throttling issues sooner). My average temperatures right now are around 65*C, and I have quite a few apps running. You WILL run into full fans and thermal throttling using videoconferencing software like Zoom or Google Meet, so keep that in mind.
I'm in the process of performing
these modifications to get the laptop to run cooler. In the meantime, if you do end up going with an Ultrawide and need to control temperatures, look into disabling "Turbo Boost" and/or limiting the fan speeds with applications like Turbo Boost Switcher and TG (for fans). The latter is probably not recommended for most, but the former is the easiest way to decrease your temperatures by a considerable amount when you're doing normal day-to-day tasks.