To broadly generalize - there are versatile bread 'n butter synths oscillators that output the typical sine, tri, saw, sqr - eg: Doepfer A-110, Tiptop 3000, Intellijel Dixie etc. Saw-core or tri-core implementations will generate slightly different wave shapes (visible on an oscillator) and sound slightly different. On the other end of the spectrum there's the specialty ones that use custom wavetables or specific sound generation algorithms to evoke a singular personality e.g. The Harvestman Piston Honda or Donut, Noise Engineering Loquelic Iteratus, Make Noise Telharmonic. Of course there are also modules somewhere in the middle - familiar wave outputs, but some extra functionality or features: Synthesis Technology`s E 350, Make Noise DPO etc.
I highly recommend reviewing as many videos & sound demos as you can to get a feel for sound & functionality and in particular would recommend visiting a specialty modular store (even if a trip is required) to try the stuff in person.
Do not panic about making exactly the right choice - it may not be clear what you will eventually settle down with until you acquire some experience with modular - and there is a great market for used gear so it is pretty easy to trade towards what will eventually become part of your own personalized instrument.
NEW EP: https://fastus.bandcamp.com/album/terra-incognito
Latest works: https://soundcloud.com/fastus
Modular studies & sketches: https://soundcloud.com/problivion