@Worx There are two ways these abilities are worded:
* Permission to play/cast a <set of cards> in a given <time period>
* Instruction to (optionally) play/cast a <set of cards>.
Technically neither grants you the ability to casts spells as an instant. The first doesn't alter the timing of playing spells at all, just gives you the ability to play them from an unusual place (the usual place is from your hand). The second instructs you to cast the spells while the ability resolves, usually you can only play spells (or abilities) when you have priority (and no player has priority while a spell/ability is resolving).
The two wordings are similar, except that the permission version lists a period of time (until the end of your next turn, while the cards are in exile, while ~ is in play, etc). Use the existence of a period of time to figure out which type of ability it is.
@RampageDon @MacedWindow Have you seen Scryfall's tag search ability? https://tagger.scryfall.com/tags/artwork/chair