Constellations are pretty easy to stratify -
1. 1st Generation (cals. 352, 354, 501, 504 and 505)
2. 2nd Generation (cals. 551, 561 and 564) - includes pie-pans, dome dial and recessed crown models, but not "C" cases.
3. 3rd Generation (cal. 551, 561,564 and 751) - includes "C" cases, monocoques, and any other model introduced after 1968.
4. 4th Generation (cal. 1001, 1011 and 1021) - includes "C" cases and any other Constellation with these calibers.
5. Tuning Forks (Accutron movements) and Early Quartz - includes "D" cases, Marine Chronometers, F300's, etc.
After that it splinters off into infinity and beyond, with not many collectible models anyway.

Seamasters are a little trickier -
1. Bumper non-chronometers (cals. 351 and 354)
2. Bumper chronometers (cals. 352 and 354)
3. Bumper calendar at "6" (cals. 353 and 355)
4. Rotor non-chronometers (cal. 501, 503, 550, 552, 560, 562, 563, 565, 750 and 752) - includes Seamaster DeVilles
5. Rotor chronometers (cal. 501, 505, 551, 561, 564 and 751)
6. Seamaster 300's (any cal.)
7. Seamaster XVI (any cal.)
Again, after these groups, Omega started to make dozens of Seamaster models per year, very few of them collectible.

I'll leave the Speedmasters to the experts.

I realize that the above is somewhat arbitrary and I've probably left something good out, or drawn other lines too thin to be inclusive.
gatorcpa

 

Is it worth adding cal 861 Seamaster chrono's to the list

 

I'd have a separate category for non-Speedmaster chronographs. You could start with the early cal. 33,3 models, right up to the Valjoux 7750 variants. This could have a subcategory for Seamasters if you want, but a lot of those models were sold in identical versions either as DeVilles or with no model name on the dial.
gatorcpa