While the filesystem used for the .iso is ISO9660 - the actual .iso file from buildiso is growing - at an alarming rate for every new build.
And using actual physical DVD media is not recommended due to the - not so fast loading DVD readers - and therefore the live image may unpredictably stall while loading the system.
The - from my POV - is using either multiboot script or ventoy - as described in this reloaded article.