Do you mean the default SD frequency on RPi, perhaps other SBCs as well?
I changed it to 100: dtparam=sd_overclock=100 => /DietPi/config.txt
Made my Pi quite a bid more responsive, I was impressed. However every source I found claims that this is dangerous for older SDcards, so I was afraid to add this to e.g. dietpi-config, if users might destroy their card and loose their data.
Would be nice if there was a reliable method to verify the card supports it 
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Btw 4K block size seems to be default on Rufus and Etcher, Debian installer and such, or for ext4. At least all my systems are at 4096 / 4K.
WarHawk
I just found above you say bs=4096 or bs=4M.
Note that bs takes the value as bytes. So bs=4096 means 4096 bytes = 4K, while bs=4M means 410241024 bytes, so factor 1024 between both results 
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The 4M in the article is about the “erase sector” size, the size of a group of blocks, that can be removed at once. The alignment of the partitions (so start and end) should be according to those sector sizes, which are given, AFAIK, by the controller, so cant be changed (?).
A “block” size of 4M is most properly not what you want. Even if allocation of data should be faster, this means that every single file (even 0 size ones) take effective 4M on the disk. So a such installed system, with many many small files, will take much more space on the disk.
However I am no specialist, so if there is indeed something we can improve, e.g. optionally in case of weak SD, would be great to know. block size at least should be up to the flash program, we just could give advices there, but I guess they already do good, know better than us. If something depends on actual image creation, that affects alignment of final written image, then this would be important to know, but I am not aware of this.