1 and 3 could both be done, 1 will reduce the number of the mysql queries performed to get values stored in the options table. WP does a query and caches all options values that are set to autoload in a single query.
1) autoload was added as a argument for options page in 5.2.8 and is listed here https://www.advancedcustomfields.com/resources/acf_add_options_page/
3) Yes, that’s what I’m saying. Use the ACF options page to make it easier to build the backend form, but then do what most plugins and themes do and store the “Real” options in an array that is per-assembled. It will slow down the admin a hair. Although, the main thing that will slow down the front end is additional queries, a few hundred lines of code will not have a significant impact. Well, depending on what those lines of code do I guess.
