"Nog" can be used in both these ways, as "probably" or "enough".
"Jag har fått nog!" - I've had enough!" (Tillräckligt don't work here)
"Har vi nog med potatis?" Or "Har vi tillräckligt med potatis?" - "do we have enough potatoes?".
I think "nog" is usually used in the negative meaning of enough, as example 1, and "tillräckligt" usually when enough is positive, as example 2.
Yeah, the "är" here becomes an /e:/ that sort of melts together with the "det" (whose t becomes silent). It's how you would say it in Stockholm. Pretend that the "det är" is like a d with a very long e. Deeeinte tillräckligt. ("Det är bra" ("It's good") = Deebra.) :)
(In the other way around, "är det inte tillräckligt?", "är det" is often pronounced "ere" in everyday spoken conversation. Ere[i]nte tillräckligt? Ere tillräckligt? Sorry.)
What a great lesson you've given us here.
We language learners use patterns & order to create a rules-based understanding of communicating. So we struggle when the everyday contradicts the foundation we've gradually constructed in this first phase of language acquisition.
Your explanation here has given me, and I'm sure others, another valuable guide to use in the real-life phase of learning to speak & understand this beautiful language.
"Att räcka" is a verb that can be used like "att nå", meaning "to (be able to) reach". Example "Sladden räcker inte till uttaget" - "The cord does not reach the outlet".
"Att räcka" is also used for situations when we consume a resource. One can sometimes translate this to "stretch" for similarity. "Bensinen räcker inte till stan" - "The petrol is not sufficient to reach the town". "Maten räcker till 3 personer" - "~The food stretch to 3 persons". The normal thing to say would be "There is enough food for 3 persons", and one could consider "räcka till" a particle verb for "be enough [for]".
(The verb can also mean "hand/pass" of something you can't reach yourself, as in "kan du räcka mig saltet" - "can you pass me the salt, please")
"Till" means "to" (or "for"), and was seen among the example above in "räcker till". Above the "goal" is specifically mentioned, but often one just implies adequacy, with or without "till"; "Maten räcker (till)." (for whatever we are going to use it for.)
-lig(t) is a common ending for adjectives/adverbs.
So the words in "räcka till" (be enough) are swapped, and the -ligt suffix added (and A dropped), for "tillräckligt".
It is not unique here to swap the words when making an adjective of a phrase. E.g. Ombytlig (changeable, fickle) derived from "byta om", vältalig (wellspoken, eloquent) from "tala väl". And as you see, the same swapping happens here in English, e.g from "speak well".