I installed the JJ2+ Version of JJ2:TSF from GOG (in my opinion needlessly clunky to start with) but can only select the resolution of 640x480 whereas my old retail disc version (standard game only, no secret files) with JJ2+ manually installed goes up to 800x600.

Also, is there a version of the Christmas Chronicles with JJ2+?

it doesn't worka t all

Also having issues, sad that this isn't getting looked into.

I haven't had any of these problems myself, but there's a chance I can help if you can give me a bit more information and/or answer some questions.

First off, are you absolutely sure you're running plus? GOG has it set up a bit weirdly, you either have to run the beta branch if using GOG Galaxy or you need to manually download it as an extra if not. And if you downloaded it separately from GOG Galaxy, you need to make sure you're actually running plus instead of accidentally running vanilla, since it's possible you've installed both and are accidentally running vanilla instead of plus.

...believe me, I've made the mistake of running vanilla instead of plus and vice-versa several times myself, I know it can happen.

But that being said, if you're sure you're all running plus, I can ask more questions from there. Screenshots proving for sure it's plus would be appreciated... doubly so since there's a chance I can get a bit more figured out on what's going on just from the screenshots alone (really unlikely, sure, but there's always a chance).

Also... BananaJane, if you're getting some kind of error, it'd be useful if you can get a screenshot. If you can't, like, if it doesn't even get that far, that's... definitely odd, but I can try to work from there to figure out what's going wrong, that in of itself could be a good place to start.

Gonna do what I can to help y'all... as somebody who rather likes the game, I can tell you right now that the game is buggy as heck (less buggy with plus but plus is still getting updated every now and then for a reason) and can be a bit of a hassle to set up on some computers, so I can't say this all surprises me, but I also find the game is quite worth getting working so I wanna help y'all if it proves possible!

I've played this game since I was very young back when it first released, and I can tell you I've never had a problem setting it up on any PC. The game has its bugs, pretty much all the bothersome ones being fixed by Plus.

The way Plus is installed via GOG is awkward and poorly-laid-out, but if you can find the buttons to do it, and you make sure you're not accidentally running the wrong version, it should work great.

This aside, I agree with your troubleshooting advice.

Also, in regards to OP's question about Christmas Chronicles -- No, but if you copy all the .J2L files from it and put them in your Jazz 2+ folder, you should be able to play through the Christmas Chronicles levels in Plus via the "Holiday Hare 98" episode in the game's episode selection menu.
The reason for this is that The Secret Files includes a file called Xmas98.J2E which tells the game to include a "Holiday Hare '98" episode, and it points the game to the level files from the Christmas episode. But it doesn't actually have the levels unless you copy them over from Christmas Chronicles. I believe if you copy a file called Xmas99.J2E from Christmas Chronicles, then you get a "Christmas Chronicles" episode, but it's functionally the same as Holiday Hare, just with a different name and artwork. The reasons for this are convoluted, and it basically boils down to the fact that Christmas Chronicles is a slightly improved European re-release of what was originally released in the USA as Holiday Hare '98. (Which is a reference to Jazz 1's two entirely distinct freeware Chrismas episodes, Holiday Hare '94 and Holiday Hare '95)

It works for me, but it's missing a lot of the music. The bass, drums, and rhythm tracks play, but the top melodies for the music tracks are missing.

I've made a thread about it here, and posted a video showing the issue:

https://www.gog.com/forum/jazz_jackrabbit/jazz_jackrabbit_1_missing_part_of_its_music

For some reason the mouse controls don't work. I set it in the controls menu for wasd+mouse1 for shooting, but after that when I press esc the ingame controls haven't changed in any way. Help!

It still shows JJ2 v1.24 in the lower left corner. How do I know I'm playing JJ2+. I installed the extras goodie JJ2+ but nothing has changed. I'm in the galaxy beta.

Edit: Ok solved it. I couldn't find the beta option in the settings but it appears to be on the far right of the screen, it was blending into the background, you will easily miss this.

As noted here, you need to get Plus, which is on the site under goodies, and in Gog Galaxy as a "Beta channel" which is in a really awkward place on the screen that you wouldn't normally notice -- all the way on the right.

This will give you 800x600. (If you're interested, there's a way to get an 800x450 widescreen resolution out of this, if you harmlessly fiddle with a graphics card setting, though it does take a bit of fenangling to get it to work right) No, but you can copy the Christmas Chronicles levels (the .J2L files) over to JJ2 TSF, and then play those levels via the "Holiday Hare '98" episode.

GOG supplies a version of JJ2 that's pre-set up with the latest version of Plus. You don't have to mess around with manually installing it, you just have to install the Plus version of JJ2 directly from GOG.

If you're downloading directly from your games library, you'll find it under extras. If you're installing it with Galaxy, you have to select a beta channel.

Look at the attachments of this post for screenshots; first one shows where to download from the site, second shows how to get to the right menu in Galaxy, third shows which option to change.

Hope this helps!

Oops. I also made the mistake of not installing the "good" version. Yup, don't download the "offline backup game installer", download the "Jazz Jackrabbit 2 with JJ2+" at the right side of the webpage!

And now, Jazz2.exe allows me to choose 16/9 resolutions. Perfect, thanks!