I am interested in such coins as nwc, cdt and mana, what do you think of these projects? Should you buy these coins?
You can get NWC coins on the KuCoin and Uniswap exchanges, they are not small exchanges, they both include international exchanges, if you are in doubt about the exchange you mean.
The same thing with cdt coin, it is listed on the pancakeswap exchange you can also get it there.
Small and large exchanges in my opinion are not immune from hacker attacks, it doesn't matter if you want to buy them on these exchanges.