First you have to take in account that APAC have more team than AMER (40% APAC, 30% AMER, 30% EMEA, I don't have data on China) and also more T2 regions. With an evolution that is really in favor of APAC (Percent of AMER go down, APAC go up)
if a region split it's will be APAC first, AMER 2nd, so you will have at least 6 regions, so you would probably have 2 slots for every region in master, and 4 in champs
But realistically, EMEA got more player than AMER and the playerpool increase compared to AMER, and when the war will be over it will increase even more. So If APAC and AMER split, EMEA will probably also split (EU have the same weigh than NA and CIS/TR/MENA largely match BR+LATAM), so you can count on at least 7 regions, maybe 8 to round it (We will need to develop Valorant in Africa someday), Master with 16 team (2 slot each), and champs with 24.
And Yes all of them would count as import