It's not really as important as all that, actually. If you are flying one of them, you know which one you grabbed. If you are flying against them, all you have to do is make sure they don't get behind you. The tactics used aginst either version wouldn't be much different.
Also, the time of the encounter will help. The SPAD 7 was a mid war airplane while the 13 was used in the last year of the conflict. If it's 1916, it's probably a SPAD 7. If it's 1918, it's most likeLY a SPAD 13.

Unless you’re flying against the French.
Going strictly be memory, and not an expert in the French Air Service, didn’t the XIII (with the lesser horsepower engine - 200 hp?) start reaching French Escadrilles in early summer of 1917?
Course now that I type that I guess I can check with the almighty internet. I’ll be back.

EDIT: Yes. Deliveries began in May 1917 - one month after the types maiden flight. And the original models had a 200hp engine later replaced by 220hp+ types.
Glad to see my memory is not going too bad!

Not to mention the fact that they did fly SPAD VII all the way to armistice. Some even preferred it to the XIII - engine less problematic.

Yea I gotta try to get into the Spads.
Great and beautiful aircraft but I have minimal stick time with the VII and none with the XIII.
Visibility thing IIRC. Perhaps I have mellowed with age.

I like the SPAD. But, yeah, visibility is absolutely awful. I lose sight of Huns I'm chasing all the time. They disappear behind that big, thick, upper wing and suddenly they aren't in front of me anymore. "Lose sight....lose fight."
The Nieuports are my favorites. The Bebe and the 17. Neat little buggies.

Yup, forward visibility is gawd-awful in the SPAD. That's why they made the instrument panel so pretty, gives you something to look at. But seriously, boom and zoom is the only way to fight in it, checking your six all the while. Get in a tight spot? Dive away, regain alt far from the fray, then re-engage. Repeat as needed or until you're out of ammo, or until the Hisso conks.