so i chose to install solus by reusing partitions including the boot(efi) partition. i didnt realise that the old boot entries would remain
im thinking the ones marked in this image are the ones. 
but theres probably more to it than just deleting the files ? i wanna do it safely too, and not just hope for the best
There is loader.conf file that list all entries from boot menu. You could remove the old boot entries from there. The files you could move to a separate folder to back up instead of delete. If it works, then remove them completely.
There's some recent threads about this: the consensus I remember is is can't be done. your firmware should be deleting them for you.
My efibootmgr is clogged up with old boot corpses, and since efibootmgr doesn't actually do anything, if you find a way to mop it up in there, let me know.
@minh that method was not one that was discussed, interesting
Check the efibootmgr cli tool https://wiki.gentoo.org/wiki/Efibootmgr
the command would look something like this:
efibootmgr --delete-bootnum --bootnum 1
you need to identify a proper bootnum
also check efibootmgr manual
