Does first one works? I have used it in past and never/ever got confirmations, doubt if they give us now this possibility.
It works but on extreme cases of network overload (like for the past few months), might take a while for a transactions with a low fee to get included in a block that they mine (since they prioritize transactions based on their fees). For a bit of network congestion, they can still be somehow useful.
I've successfully accelerated transactions with fees as low as 1.5 sat/B (in the past).
Also I can add btc.com's accelerator but maybe it don't worths, their fees sometimes are more than bitcoin value in usd of whole transaction including it's low fees.
Same can be said regarding ViaBTC's paid option (they give prices based on the transaction size itself, not its value).