Unlike camera lenses, where choice of focal lengths is substantial for any given negative size, you're quite limited in the darkroom. You can go longer, but hardly shorter on focal lengths for a given negative. I don't know of any enlarging lenses for 4x5 below 135 (although I would not be surprised if there are some with satisfactory coverage), which as stated already is going to give you the largest print size for same elevation.
There is a Rodagon WA 120mm wide angle lens for 4x5.
There may be other wide angle lenses out there, but I do not know of them.
The WA lens will give you a bigger image for a given enlarger height.
So 120 biggest image, followed by 135, then 150 with smallest image.
But the cost of the WA lens is much more than the standard 135 or 150.
In my case, I have a 135mm lens for my Omega D5, rather than the 150mm lens.
This is because the D5 has the shorter standard height column, vs the D5-XL with the taller column.
The gain from 135 to 120 will be 12,5 %. So on linear dimension, it should enable one to change a 16" x 20" image to 18" by 22,5", for example. From 150 to 135, the change is slightly less, but it may be such that one can fit in a paper one size larger that isn't possible with the longer lens. If you use WA lenses, make sure that your bellows assembly contracts short enough to attain focus at all column settings. I cannot for instance use a 40 mm lens for 35 mm on my Durst M605. Although I have no idea, it may be possible that some 4x5 enlargers do not allow for such short lenses to be used, unless they were designed for all image sizes down to 35 mm, or at least one or two formats down.
If an enlarge is spec'ed as limited to 20"x24" and shorter focal length lenses are used, does the condenser/diffuser limit the size of the print? I am just wondering about limitations caused by a condenser or diffuser.