The download and install guide is fairly out of date, but still has useful info on most mods out there...

If 1.13 is your bag, you still have the ever present AIMNAS, Deidranna Lives and Urban Chaos among others in 1.13 form. More recently there has been releases of Arulco Vacations and Vengeance:Reloaded to choose from both of which have their own threads on here for more info.

For Vanilla JA2 (and Unfinished Business derivatives) there are plenty of mods that are acquiring cobwebs, but still quite playable, once again check out the download and install guide.

1.13 is constantly evolving, with both stable and unstable releases. Seven FM also has an experimental build that uses the older 7609 build but with AI improvements among other things, so you have plenty to evaluate.

Welcome back to JA2, Victor!

The new features are added to the latest (unstable) builds by the current modders. Usually there's a mention in the description from which build on you can find that new feature added. Until used in a true sequel/mod they are just v1.13 features, valid only for default game. If a full-blown mod is built on version XYZ, then it will include the "new features" XYZ had.

The full blown mods are another cake completely. In the majority of cases they are built on a specific v1.13 version and they work only on that one. Mixing them with other versions is possible but risk of messing them up is very high. Due to the nature of the beast keeping full-blown mods up to date with v1.13 releases is pretty much impossible.

PS: "Unstable build" means just that that's a version in continuous development, while "stable" is a version that's published once in a blue moon, in theory stable enough to be used for sequel building. For regular players though, especially those looking to test all the new additions, "unstable" v1.13 is fine.