You shouldn’t need to increase max file size just to import a site. All Local needs to import a site are a zipped up copy of wp-content and sql. You would use a free plugin like WP Migrate Lite to simply export a full site copy and then import that into Local.
That being said you do have the ability to edit PHP values in Local. These values can be edited in the php.ini.hbs file within the site’s conf/php/ folder. SImply open that file up in the text editor of your choice, save your changes and then after making any adjustments, be sure to stop the site and re-start it so that Local can compile and use those new settings.