Although you mention using Auto, note that P (Professional, sometimes mistakenly called Program-Auto) is exactly the same as 'Auto' with the ability for you to dynamically adjust those camera-determined settings. Say the camera selects f/5.6, the human Professional can dial to f/3.5, available with their professional f/2.8 lens, and the camera dynamically adjusts the shutterspeed and / or ISO to maintain the same exposure. If you have some sort of fetish about counting images, this may be the approach to consider.

What is important is that you achieve the image you desire. No cares, no one on UHH, not your grandmother, not your life-coach, NO ONE cares how many images you took. We all only care about the final result you achieve.

A possible test for you. Mount your 10-20 on your D500. Set lens to 16 mmm (16 x 1.5 + 24mm equiv.) and take a couple of shots.

Then set the lens to 18-19 mm (28/1.5 = 18.66 mm) Step backwards until you have the same image framing as you had with the lens set at 16 mm. My guess is it will be about 3'-5' distance between the two. Then you know that by stepping back a few feet, you can have the same image with either lens.

Then you can decide if the 1.4 version of either lens has a big difference in cost and what amount of money you want to spend on a 24 or 28 mm f1.4 lens.

Good luck with your testing, decision and purchase plus future image making.

When I was a photojournalist before dirt existed I used two lenses, the Nikon 200 f4 and a 24 2.8. OH, and a Nikon F.
You are cutting hairs between the 24 and 28, I strongly suggest before you buy either of these high quality lenses you go somewhere where you can put them both on your camera and try them out.
To be honest with you, I have owned them both, what do I use now?, the 24 and 28 1.8 E. They are both as sharp and with your D500, a high quality producing ISO camera can easily handle the very low difference in F stops. There just is not that much difference between a 1.8 lens and a 1.4 with todays high quality ISO camera's to justify the price difference. Back in the day when you had ISO Tri-X 400, YES, 1.4 meant something because the alternative was only a 2.8 lens. But today, YOUR THROWING YOUR MONEY AWAY.
And I can get as much bokeh with the 1.8's as I could with the faster versions. Take it from someone who has owned all four, you almost better off with the newer E 1.8 versions. Honestly.