Let's say I am an holder (min 3 month). The altcoin I found are not listed in famous one like Binance. They have really low market cup: 100k.
At the moment I am just seeing them on Coinmarketcup and would like to start selecting them by the exchange they are listed.
So I would like to understand if the exchanges are good or not.
How should I interpret the volume and liquidity values for the exchanges?
most exchanges are not good. what you can do Is buy altcoin on those exchanges that you mentioned and then withdraw and leave in your wallet until it is listed on some big exchange like binance and other good ones. It is common knowledge that most exchanges are not good, but charge low listing fees, which is why many new altcoins list on these exchanges that are not good.