So, I'm sure my answer lies somewhere within this 22 Page post, but I'm lazy...
So, the question is...
Are the spells that are offered in either supplement book allowed no matter which book you chose for your origin?
Meaning, I play a character with the SCAG cantrip option of Booming Blade, can I still select EE spells as he levels, or are those in essence locked out of my character?
Advanced Logsheet Tutorial
Elemental Evil Characters and Character Rebuilding
When rebuilding your Elemental Evil character, pay close attention to spell selection and race choice. As stated in Sword Coast Adventurer’s Guide and You!, Elemental Evil characters can only use options from either the Elemental Evil Player’s Companion/Princes of the Apocalypse or the Sword Coast Adventurer’s Guide.
Wizards (and other characters) cannot therefore choose spells from the EEPC when leveling, while also using cantrips, races, ethnic languages, deities, domains, class options, or backgrounds from the Sword Coast Adventurer’s Guide. They can however, learn such spells by copying them from a scroll or spellbook, or as an adventure reward in some adventures.While deep gnomes are available in both products, this unfortunately means that genasi and goliath characters can never take advantage of the options in the Sword Coast Adventurer’s Guide.
No. When playing an EE character, you choose one of the two products (EEPC or SCAG) and add that product to your "Allowed Rules" list. The other product is forever barred to you. You cannot choose anything from it, even when leveling.
You can however, learn spells from the EEPC if you find them in a scroll or spellbook, or copy them from a fellow PCs spellbook (who chose EEPC instead of SCAG). As a result, EEPC spells will become increasingly more rare in the near future, as many players will choose to respec their EEPC spellcasters, removing those spells in favor of SCAG materials.
So, if I chose SCAG as my starting resource, I can't add spells from EEPC unless I "find" them during a module, via a spell book or scroll?
What about when I level, can one of the two spells that I learn as I level come from EEPC?
Can I purchase them in a EE module if there is a store that offers them?
Are the spells that are offered in either supplement book allowed no matter which book you chose for your origin?