They should be more reliable than most of other alternatives, but none of them should be fully trusted.
they use the perpetual swap model, same as bitmex. it's not exactly an alternative to binance or bitfinex, which are simpler to use and understand.
the liquidity is also poor on kumex compared to larger derivatives platforms. the spread alone is 0.15% during non-volatile times, let alone during violent moves. i would be wary of taking out large positions there.
with deribit rolling out mandatory KYC next month, i'm hoping kumex will pick up some of their customers though. we'll see.