The PlayStation Plus Premium should largely copy what has already been offered through the PlayStation Now service separately. And it is to be expected that the games offered with PS Now will become available on PS Plus Premium. However, as Reddit users point out, 56 titles from the current PS Now offer have an expiration date, after which they will disappear from the offer. And it is questionable whether Sony will extend the agreement with the publishers of these games to make them appear in the PS Plus Premium catalog.
Among these games there are several classics, there are among others Metal Gear Solid 4, Castlevania: Lords of Shadows, Silent Hill HD Collections, Yakuza games, Crazy Taxi, Sonic Forces, Sonic Generations, and other Sonic games. Metal Gear Solid 4 is especially interesting as a game that cannot be played on today's consoles in any other way than through streaming, ie as part of a subscription. Other options are to emulate the game on a PC and play on the PlayStation 3 console.
Sony has not yet revealed the list of games it will offer in the catalog for PS Plus Extra and Premium subscription ranks. There is still hope that Konami, Sega, and other publishers will agree to continue working with Sony and make their old titles available at least by subscription. When we don't have a remaster of Metal Gear Solid 4.
By the way, the Digital Foundry channel yesterday launched an analysis of what an MGS 4 remaster would look like today, demonstrated through emulation of the game in 4K resolution at 60 frames per second. Worth seeing: