Based on my own experience, yes the weakest link in the chain is the highest you can achieve. But even the Max xfer speed numbers you quote will be the max possibly achieved transfer speed but not necessarily what you’ll actually achieve. A simple file transfer on a relatively cleanly running M1 MBA? High likely. An expansive app accessing the SSD? Probably…maybe. If a whole lot is going on your M1 MBA such as unfriendly webpages open, YT, maybe other things, and especially if your SSD is getting into the full-ish range? Don’t bet the mortgage payment on achieving max xfer speeds. If you have 16 GB RAM? That’s very helpful for the subject of xfer speeds. That’s because swap memory is pretty commonly used by operating systems, certainly on Apple Silicon MacBooks (maybe not so much on MBP 14 & 16 stocked with unified RAM). The swap resides on the SSD (to quickly and very generically explain: flash memory makes up an SSD). But as mentioned the SSD is getting full AND a lot is going on (web pages galore open). See the negative loop there? The OS (and app) needs RAM—>RAM may use the swap—>swap lives on the SSD—>to ‘process’ the write to the SSD the swap on the SSD is needed.
That is not only an Apple thing, not even remotely only Apple. And most importantly the max xfer speed will not be needed for what most buy an MBA for. But if you have a workflow that is a lot of intensive renderings, trying to play graphic intensive games and frequent huge file xfers, MBA or MBP 13 is just not the right choice imho. I happily own the base 8/256 MBA M1. Swap using the SSD can spike. Xfers and most everything else zips along for my usage. BOL