Digital Track and Analog Track
SCX Digital track can be used with SCX Analog but you cannot use SCX Analog with SCX Digital because the grove is no deep enough. They changed all the track to SCX Digital so that is the best quality track and a little bit wider. They have a converter track available in all the sets. If you do have a bunch of SCX Analog track you can buy this set “https://protinkertoys.com/collections/1-34-race-sets/products/a10111x5u0-scx-1-32-scale-slot-car-set-original-system-set-c1
“ which comes with a converter track so you will be able to combine all the track.