Confirmtx is a dubious choice, because we don't know whether or not they actually have partnerships like they claim with btc.top, antpool, bixin, basically all the leading pools.
Bitcoin.com pool says that they have absolutely nothing to do with them, yet they said that they had a partnership with confirmtx. But since it's free up to 400 bytes, you could probably try it out anyways. But definitely don't pay for their services.
For me, antpool's acceleration service is the best and quickest. You need an account though:
https://www.antpool.com/user/prioritiseTransaction.htm?m=savePrioritiseTx