The original Secret of Mana comes to mind. The game was originally meant for the Nintendo Playstation, and when they had to cut a lot of the games content in order for it to fit on a SNES cartridge. On top of that, the English translation for the game was completed in a month so the game could be released for the holidays.

I don't interact enough with the Castlevania fandom enough to know what the fandom consensus is, but my personal recommendation to start with (for the large map-based games anyway) is Aria of Sorrow. I mostly just love the fact that you collect enemy souls in the game. I just love the blue mage archtype and I think anyone else who plays it will think its pretty cool.(Igarashi thought so too as this was the only map based game to get a direct sequel and the soul collecting was recycled in Bloodstained:Ritual of the Night).

One thing i dislike most with the map based games is how strange getting a true ending can be, and Aria is probably like the least bad. You need to equip 3 specific souls when you defeat the final boss, and you get hints around the map telling you where they are. It can still be annoying to find them and soul drops are random but its still a much better requirement than some others.

Also the GBA games are the only map based Castlevanias on modern platforms, so honestly you might as well.