Is there a way to upgrade the 64 model to 256 (or more)?

"It would require a hot air soldering station to remove the flash chip. The chip is then put in a reader and cloned to a new similar but larger flash chip. Some editing to the partition sizes before the new chip is installed back into the quest.

It could cause issues when going to storage levels above native options though. Updates might cause problems or Oculus/Facebook might detect the modification."

yes download more ram

Unfortunately, the Oculus Quest 2 does not feature any user-upgradeable components.