Signing 100 extra transactions would only require an additional 6400 bytes. Even with a slow connection speed of 100KB/s, transferring this amount of data would take just 64 milliseconds, with latency being the dominant factor.

Regarding RBF (Replace-by-Fee), it has a default minimum incremental relay fee of 1sat/vByte. By using the 100 pre-signed transaction variants to sign every possible minimum incremental relay, a range of 1sat/vByte to 100sat/vByte can be covered. This range is believed to be sufficient for getting mined for any block in Bitcoin's entire modern history.

On the other hand, CPFP (Child-Pays-for-Parent) requires two transactions and therefore requires extra bytes. Unless dealing with very large transactions in low-fee environments, there are no circumstances where CPFP outperforms RBF.

For more information on this topic, you can visit Peter Todd's website at https://petertodd.org or contact him via email at 'peter'[:-1]@petertodd.org.