Probably this is one of the reasons for poor perfomance of n64 in pi4.
And dreamcast have the same problem with the videomode.
Would be interesting for testing, that someone with a pi4 or rpi400 do the videomode change test with n64 and dreamcast to see if it works, checking always the final resolution in tv or monitor, and if works post the options used.
I resized it down to 800Mb and that completed the first boot successfully
Sorry, but this is not how it works: if the system did not create the SHARE partition, your night was not successful, probably the problem is the quality of your SD card, I recommend testing with another one.
You should not change the size of the main partitions, the only partition you can shrink is the SHARE partition if you want to use dual boot with another system. the partitions are the necessary size, there is no "needlessly left", the space is "reserved for updates / temporary files / etc", there is a reason, it is not an error.
That's great news. Thanks for your answer and for your time and hard work.
PS. Is it difficult to add the alsa mixer in F4 console like in batocera? I think it could be useful to have it right there.