For the 688, you'll want the H-B "3 in 1" kit. Build the Flight 1 version but don't use the "Flight 1" stern planes. The "3 in 1" kit has been reissued and you should be able to find it online. Don't use the DSRV "target" decals.
For a realistic build, only use the draft marker decals.
Check the resources thread and you'll find a link for 3D printed screws in 1/350th scale. They are remarkable but also very delicate.
The H-B Alpha is probably available online. Its a toss-up between the Alpha and the Typhoon, H-B reissues them every couple of years and you'll probably find them on EBay or Amazon. The H-B Typhoon in 1/350th scale has only been released once as far as I know but it should be due for a re-release.
Whichever of the two kits is more scarce can cause some headaches or price gouging. Try Amazon first then use EBay as a fall back. A company named Mikro-Mer also offers an Alpha in 1/350th scale but M-M is located in Ukraine.
M-M kits are great in terms of scale but they aren't at the same level as H-B in terms of "shake the box and add glue". You'll need some basic modeling skills and several cans of beer.
BE AWARE THAT H-B ALSO RELEASED THE 688 AND THE TYPHOON IN 1/700TH SCALE. ALWAYS CHECK AND MAKE SURE YOU'RE BUYING THE RIGHT SCALE.
The fixed cleats on the back of H-B 688 are a pain-and-a-half. Check the Resources thread where I wrote about how to use shirt pins and a file to make your own cleats.
This will save you a lot of time and frustration and I can almost guarantee you'll lose one or more of the H-B cleats.
Painting is pretty straight forward. Find a jar of Tamiya Titanium Gold (X-31) as the basic color for the screws on all three kits. You can also play around and add some silver or brown but X-31 is already pretty close. Semi-gloss black is also a good fit for the topsides of all three kits.
For the 688, this is a case of where I can't un-see what I already know. All 688's use Insignia Red as the "red lead" under the water line. That water line is also tricky if you want an accurate build. The waterline is basically 20 feet above the keel, however ALL 688's also use a 2 degree up angle to mark the water line. So, if you want accuracy, get ready to spend some time laying out the masking tape.
For the Soviet boats, try a more "European" color of red lead or else try Tamiya's Nato Black (XF-69) or German Gray (XF-63).
BTW, don't forget the USS Pogy.
Miko-Mer has a nice selection of 594 and 637 class US boats.
You'll want a 594 class sub to be the Pogy.