One curious idea my friends have entertained is to go one level even deeper and emulate the very transistors that make up the NAND gates on the web, too. It would certainly spell disaster for performance, but it's without-a-doubt interesting.
If not, I think a NAND gate is made of just two transistors, so if you mean emulating how transistors should behave then I don't think it will affect performance more than ~50%
In https://nandgame.com/ (mentioned elsewhere, a game version of NAND to Tetris) you start by making a NAND gate out of relays. The relays are electromechanical components, but you can choose to think of a transistor (within certain "regimes") as being directly electrically equivalent to one. (This simplification isn't appropriate for all engineering tradeoff purposes, although I don't know the details of how it fails or how we can benefit from knowing more about transistors' actual behavior.)
The electromechanical relay is a very simple device to understand, if you're willing to just believe that electromagnets produce magnetism (without understanding why the universe works according to Gauss's laws on the relationship between electric current and magnetism). It's a coil of wire where an electric current produces magnetism that physically pulls a switch open or closed.
A few nand2tetris fanatics have actually done this! And by a few, I mean quite a lot of people. Here's one such hardware project of nand2tetris: https://gitlab.com/x653/nand2tetris-fpga/
