For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
Sorry, tables added by a Sales Force User - objects with names ending in __c. They function as normal tables in most ways with a set of standard fields like Fabrik.Not sure what you mean by standard tables vs custom?
-- hugh