Ooh, good catch! Looks like I missed adding that to the style. I've fixed it on GitHub, and I'll upload it again here shortly; in the meantime, you can see the fix here on lines 67-68: https://github.com/shawna-p/EasyRenPyGui/blob/main/game/screens/dialogue_screens...

If you're ever having trouble finding a style property (like the size of the font), don't forget you can hover over it and hit shift+i to get the Displayable Inspector! If you do so hovering over the name, it'll tell you that the size comes from style say_label, which you can then search the project for and find in the dialogue_screens.rpy file (which is where the fix went!).

The save directory starts as None in the template, which means that Ren'Py will only save files inside the base game folder (and doesn't make an additional, "special" backup in AppData or similar - depends on the OS). You should give it a unique name so it can make that extra backup folder - typically, Ren'Py auto-generates this, but since this is a template, I can't auto-generate them for each new person who downloads it. So it's up to you to fill something out there. 

The name itself just has to be a string, but keep in mind it has to be unique, and probably shouldn't contain spaces or special characters to avoid problems. A typical save directory name, as noted in the comment above that config value, is something like "FreshProject-4689753165" (quotes included, it's a string). FreshProject is probably the name of your game - BaldursGate or ANightInTheWoods or whatever - and then the numbers can honestly be whatever; by default they're generated from the timestamp the project was created at so it's unique, but you'll have a fairly equal amount of making a unique name by just smashing together however many numbers you want.

This name isn't really visible to the player! It's just a special folder for saves and persistent info - they can find it if they need to, but it mostly exists behind the scenes as a backup for their saves. Basic rule is to use the name of your game with no spaces or special characters (so no &, exclamation marks, periods, etc), and then do a dash and just keysmash some numbers to the end of it. Once you've set it you should generally not change it. Hope that helps answer your question!

No worries! So the main menu buttons just take the regular button style, in styles.rpy - style button and style button_text. Changing that will change all buttons that inherit from it, so if you want to just change the style on the main menu, I suggest you write style_prefix "mm" on the main_menu screen, and then your buttons will have the style style mm_button and style mm_button_text, which you can adjust however you like. You can also directly assign a style to a given button, e.g. textbutton _("Start") style "main_menu_btn" will make that button use the styles main_menu_btn and main_menu_btn_text. Hope that helps!