Can you configure a form from a custom pop-up?
Not really, no.
I've a number of similar layers that contain text boxes that colour in-line with the symbology in HTML, or Arcade to format and change grammar in a box, along with using tables to hold/format data. I also have expressions to determine other calculations. When in a map and you convert pop-up to form these elements do not come across.
So, with this in mind, I usually just build in Field Maps knowing I will still have to do the pop-up work, but that's nearly all copy/paste, copy/paste. (Just like below)
@DonavanSnow, Jonathan is right. You can click the convert from pop-up button which will carry over a lot of the styling and settings in the pop-ups (whatever fields you selecting, grouping, etc), but the arcade expressions are not always 1:1 so you'd want to copy and paste those in after the fact
