if recalbox still runs slower on the n64 games you could try installing it on a pc 32 bit or 64 bit.
32 bit pc's are built before 2010 and64 bit pc's are built after 2010. you can go to the download link here for dragoblaze 32 bit/64 bit. https://archive.recalbox.com/ i have installed it on my pc using the 64 bit version and runs n64 games alot nicer but still lags at times using a clean 4gb of ram. if this doesn't solve your problen you can go to my page about running n64 games on recalbox.