The power specifications are often given by the manufacturers in a way that is somewhat difficult to understand. In principle, it depends on the power that a monitor can send to the notebook via Power Delivery via USB-C. It is often difficult to read from the technical data whether it will work without problems with your own notebook. Charging is certainly possible, but whether fast charging is also possible is not always 100% guaranteed. It also depends on the USB-C cable, i.e. it should also deliver the power that comes from the monitor via PD. Dell has a model on offer that would offer a much better resolution, so 90 watts via Power Delivery is definitely better than 65 watts, and the risk of problems with charging is definitely present with only 65 watts via Power Deliery.
I would also choose a 3840 x 2160 pixel resolution, because with 3440 x 1440 pixels you have much less screen space. A 32 or 42 inch screen with 3840 x 2160 pixels would definitely be better for a MacBook Pro 2021, because the Macbook panel is also very high resolution. With 3840 x 2160 pixels, you can see as much on the external screen as on the Macbook and the texts are much sharper, even small fonts.
This Dell model can deliver 90 watts via USB-C and would certainly be a good choice:
Dell UltraSharp U4320Q (42.50 ", 3840 x 2160 Pixels)
