Welcome to the gang! Glad you got your first one under your belt.
It looks like Alex gave you a very comprehensive answer that I hope helps.
From someone who is still relatively new, one thing I could not encourage more is to over shoot. Especially when you are new, it just takes a minute to get a couple of images of even small spaces.
I’m amazed that you didn’t see an issue when you went to align the image.
One thing I’ve found is, if my tripod shifts I immediately see an issue on the floor plan. The walls will not match and I can see ‘mirroring’ (for lack of a better work) where a wall from one pano slightly misaligns with the same wall in the other pano. As soon as I spot this I simply re-take the images. (if you have not done that, simply select the image you want to retake by pressing that image on your iPad/phone, the system will warn you ‘do you want to overwrite?’ press the ‘You Betya’ button and you’re on the the next image.)
A big help (again at least for me) is to have a 10 inch iPad. I honestly don’t know how folks do this on a phone. It’s just so tiny. With the iPad, when I load the project into stitch, it only takes a couple of minutes to tighten up the floor plan, so I can upload it to the portal. Hope that helps! Please feel free to reach out if I can ever help! We all have to learn and it’s normal to make a few mistakes at first.