Which Nintendo Classic to buy?

Yes. 30 built in games. Does not have a cartridge port though.

https://www.nintendo.com/nes-classic/

No, there is not a version of the Nintendo Classic that has both the pre-loaded games and a cartridge port.

I believe that at one point there was a Nintendo game cartridge made by a third party that (supposedly) had over 50 games pre downloaded onto the cartridge. Although it did indeed have 50 games all of the titles on the cartridge were crappy and poorly made.

If you want “a Nintendo Classic that has built in games and a cartridge port, all in one” then I suggest you just buy an NES mini, although it doesn’t have a cartridge port it still operates very well and has almost every NES game ever (To my knowledge.).