Two, both digital:
Standard - $79.99
The game. Pre-orders placed before November 20 add the Vintage Vice City Pack, a set of in-game items rather than any change to the game itself.
Ultimate - $99.99
The game plus additional in-game content. It does not buy early entry, a different version of the story, or a separate build - the extras sit inside the same game everyone else is playing.
Editions that do not exist
Deluxe. Special. Collector’s. Premium. Each of those appears regularly in search results, on YouTube thumbnails and occasionally on grey-market storefronts, and none of them is real. Rockstar published a two-tier lineup and has not added to it. Nor is there a boxed set with a map and a keychain, because the game has no physical release at all.
If a page is selling you an edition Rockstar has never listed, it is either an outright scam or a regional key with a story attached. The check takes ten seconds: open the PlayStation Store or Xbox Store product page and see what is actually offered.
Which one to buy
The gap is $20 for cosmetic and in-game extras whose full value is hard to judge before release. If the extras are things you would otherwise buy later, Ultimate saves money; if you mainly want the story, Standard is the whole game. Nothing in Ultimate is required to finish anything.
On the PlayStation side
Pre-ordering there also includes a month of GTA+, which is worth factoring into the comparison if you were considering the subscription anyway.
Price detail sits in our answer on how much GTA 6 costs, and store changes get reported in the news section. For the full breakdown of every edition’s cost, check the price page.