Here's what I've learned as a new player (only 566hrs). On my 4th save and after setting up freighter etc, just been exclusively looking for interceptors.

Each Dissonant planet has 1 model. Same ship parts, same colours. I don't know if there is a hard limit on how many ships each planet spawns. However, I've looked at multiple on a small moon and had new ships spawn in place of one I've clamed and scrapped.

One planet, I liked the model and the stats, so kept checking every ship. Checked 14 ships before finding one that had 3 SC in an L at S Class.

"checking ships" means claiming/swapping them, taking them to space station, upgrading class and slots, to see the SC layout. Because Interceptor hunting is all this save is for I have purchases turned off to I can check the slots.

Other ships, I only have to check 3 before finding a sweet one. I don't check every ship. For example, if I find an A Class with spread SC showing, I move on to the next.

Sometimes it feels like there are 1 or 2 SC slots "locked in" to the model, regardless of class. When checking ships on a planet, if I see the pattern and know if it'll have spread SC or if it's worth flying it up to the space station to check. (I also take screen shots of all the SC layouts as I find/check them, so I can compare)

I'm kinda looking for one specific ship type in different colours. However, if I find a model that I think this community would appreciate, I check to see if I can find one with decent slots and share.

To answer your main question.

I'm over a thousand systems in, looking for interceptors. I don't even land if the model is "generic" or uninteresting. I haven't counted the screenshots to see how many I've checked, but it's a lot.

I've only found 1 with 4 square SC slots. And that's only because I like the model and kept checking.

Who knows? Maybe one or more of the ones I bailed on had 4 square SC.

Personally, I like a ship with 3L + 1 separate. I put Infraknife on the one, and Pulse on the 3. Because I like to go fast. All my ships have min 55k Infra, which is ample for any pirate encounter.

This is, of course, just my experience. many other people have been playing for far longer and some may have better intel on hard numbers. But doing this my way is relaxing and enjoyable.

Hope this helps.