The second OP quote (footnote about the mystical streak) refers to a meeting with Wittgenstein by Anscombe herself. For an account of Wittgenstein's relation to the Vienna circle philosophy see Stern's Wittgenstein versus Carnap on physicalism.
As for Carnap, Anscombe most likely refers to his self-account of meetings with Wittgenstein in the Autobiography, see extended excerpt on Waggish. However, Carnap's remarks seem to be based more on observations about Wittgenstein's personal style than analysis of the Tractatus:
"His point of view and his attitude toward people and problems, even theoretical problems, were much more similar to those of a creative artist than to a scientist; one might almost say, similar to those of a religious prophet or seer. When he started to formulate his view on some specific problem, we often felt the internal struggle that occurred in him at that very moment, a struggle by which he tried to penetrate from darkness to light under an intensive and painful strain, which was even visible on his most expressive face. When finally, sometimes after a prolonged arduous effort, his answer came forth, his statement stood before us like a newly created piece of art or a divine revelation... For us the discussion of doubts and objections of others seemed the best way of testing a new idea in the field of philosophy just as much as in the fields of science; Wittgenstein, on the other hand, tolerated no critical examination by others, once the insight had been gained by an act of inspiration...
Earlier when we were reading Wittgenstein’s book in the Circle, I had erroneously believed that his attitude toward metaphysics was similar to ours. I had not paid sufficient attention to the statements in his book about the mystical, because his feelings and thoughts in this area were too divergent from mine..."
Carnap's interpretation of "shown, not said" and "what can not be said must be passed over in silence" is, perhaps, natural in the light of his personal observations, but it is controversial, and many modern scholars find the "mystical interpretation" to be dubious. Rather than talking about "ineffable truths" that can not be expressed, he is more naturally interpreted as talking about linguistic confusion that Tractatus is meant to dispel (the so-called "resolute interpretation", see What did Wittgenstein (mean to) achieve in the Tractatus?). The "ineffable" is trying to express that which is simply not there, falling into a trap of empty language, Tractatus is a way "to show the fly a way out of the bottle", "showing" is doing in practice, instead of talking. In any case, this is the direction Wittgenstein's thought took in later years. So Wittgenstein might have been closer to Carnap on substance than the latter thought, see Nonsense and Clarification in the Tractatus by Kuusela:
"First, instead of providing us with a paradoxically nonsensical doctrine the Tractatus aims at demonstrating that the clarification of philosophical problems requires a particular approach to philosophy, which differs importantly from how philosophy has been traditionally conceived. More specifically, according to Wittgenstein, philosophers have made a mistake in treating statements concerning the essential, i.e. necessary features of things as if they were simply another type of statements of fact..."