Indeed, the graphics for the character select screen are bugged, but the classes look fine afterwards.
The Monk doesn't wear any armor: the game is balanced around him being fairly weak defensively. He will get armor points as he levels up.
As for grinding: the game is balanced to take on Garland at level 2, the Pirate cave at level 4, the Marsh Cave at 6 and finally Astos at 8. This does mean a little bit of grinding, but you always have the challenge of trying to beat them at earlier levels. One of the biggest complaints people have about the PS1/GBA versions is that you level up too fast. The way the game is now, there's room for exploring and fighting around without the the danger of making the game too easy in the long run.
As for grinding for gold: it's very expensive to buy everything and while doable if you get all the chests, the game lets you keep a challenge by going onward without 'perfect' equipment.
Thanks for the feedback!