Removing the wrapping newline from the FASTA/FASTQ convention also dramatically improves parsing perf when you don't have to do as much lookahead to find record ends.
Unfortunately, when you write a program that doesn't wrap output FASTAs, you have a bunch of people telling you off because SOME programs (cough bioperl cough) have hard limits on line length :)
I've only tested this when writing my own parser where I could skip the record end checks, so idk if this improves perf on a existing parser. Excited to see what you find!