I forgot they have a 30 day trial, so gave that a whirl. I tried to double a jpeg so I should get a 40 in x 20 in print. It took about 3 to 4 minutes on my Ryzen 7 with 32 GB RAM - so not 1 I'd do unless I had to. The photo was taken with an original E-M5 - so High res wasn't available. I also didn't know about jpeg/RAW difference, so i was pretty green. I can crop a portion of each photo if anyone is interested.
Oddly enough - the top phenom II CPU has a higher score than my Ryzen 7. Not bad for a 2009 CPU. I considered the Ryzen 9, but cheaped out. Mind you, the Phenom II X4 uses almost 2x the power. I actually decided to upgrade pc after using Topaz sharpen AI. Great results, but I'd go get coffee while my first gen i7 worked away.
If your panorama consists of 20MP (or even 16MP) vertically oriented shots that are stitched together for your pano, a non-upsized image should be just about enough for 4' x 2'. As usual, it's the vertical dimension that is the problem (unless you took multiple shots in the vertical dimension as well as horizontal too). With a 20MP camera you have 5184 pixels to print at 24", which is 216 ppi (pixels per inch), which is often enough.
Of course, this assumes perfect results when the pano is done. You'd probably have to crop some off the top and bottom of the initial stitching, so you lose some, and if you used a 16mp camera, you'd have even less. Looking at a very wide pano I took in Utah with an E-M10.1 (16MP), the result was 19370 x 4188. So if you printed 4188 at 24", you'd be printing at 174 ppi, which might be fine, especially at the normal viewing distance for such a large print. I have sometimes printed images at 150 ppi and they look very good.
What I'm saying is that you might not really have to upsize, and if you do have to do some, a regular image editor might be enough.