To be honest, I was pretty shocked as well when I discovered that Scissors & Planes models don't come with model-specific instructions or at least hints on what parts go where. On the A-4 Skyhawk model I even ran across an uncorrected error in the design (the gap between the wing upper surfaces was too narrow to fit the fuselage), struggled with it for a while, and only then figured out where to look and found a photo that showed the fix (split the wings down the middle) buried in the main S&P thread.
Here's the post in that "One model per (non-working) day" thread that shows the first completed S&P A-1 Skyraider. There's a another post a little further on that shows another variant.
As CMDRTED said, the trade-off is that Bruno has designed nice models of an incredible number and variety of prototypes.
So yep, building an S&P model typically means looking for it on the S&P thread, searching the Aviation and Kit Reviews forums for posts by others who've done a build before, and searching online for photos of the real thing to reference. It helps to do the latter anyway since S&P planes don't come with formers to control the shape, so, as you've no doubt found out, assembly requires a lot of pre-forming.
Here's a post kggmodel made a few months ago that links to all of Bruno's existing test builds. If clicking the links there doesn't take you to the right spot in the thread, make sure your site user preferences are set to the default 10 posts per page.
Scissors & Planes has models available beyond what's on ECardModels, which I've seen others say can be ordered via direct message to Bruno's
scissorsandplanes account, though personally I haven't tried that route.
Here's the S&P 1/100 model catalog as of June 2022.
Here's a graphical list of model profiles from a year ago.
Also if you go to the Aviation forum and
click on the paperclip logo for the "One model per (non-working) day" thread, it shows you all the attached files from that thread, mostly 1/300 scale.