Schwa or ʊ or ɪ

[keannu]

I heard in numerous cases the following syllables pronounced unrecognizably.
In many pronunciation websites, they teach when there's no stress in the underlined vowels, they change to schwa(neutral sound, not ə but the sound as in tomorrow when o sound disappears)

but they seem to pronounce these as "ɪ" or "ʊ", did I mishear them? There might be some difference between AE and BE, and I'm afraid if I can learn correctly through writing explanation not sounds in this website.
ex)Electrical, Eleven, Event

[5jj]

LPD gives both /ə and /ɪ/ for eleven, event and electric, but only /ɪ/ for electrical.
The Cambride EPD and the Oxford ALD and COD give only /ɪ/ for all of them.

None gives /ʊ/, which would sound very strange to me. I am an /ɪ/ man.

[keannu]

LPD gives both /ə and /ɪ/ for eleven, event and electric, but only /ɪ/ for electrical.
The Cambride EPD and the Oxford ALD and COD give only /ɪ/ for all of them.

None gives /ʊ/, which would sound very strange to me. I am an /ɪ/ man.

Okay, I got it, I must have heard either schwa or /ɪ/ for them. Does it have any BE and AE difference? I think not.
And I think you must know the difference /ɪ/ and /i/.and something that bothers me is some e as in "excuse, Engish" sounds like /i/ as in eat[i:t], but some like eleven, event, electric sound /ɪ/ . There seems to be no rule for so many /e/ spelled sounds, or have I heard wrong for either of the two groups? I don't know which to choose to pronouce when I see e spells.

[5jj]

There seems to be no rule for so many /e/ spelled sounds

There is a certain correlation between some letters and sounds. For example, the sound /m/ is normally represented in writing by a single or double letter m, and the letter m normally represents the sound /m/.

However, there is very little correlation between other letters and sounds. Note the pronunciation of the letter e in: pet, pert, pretty, Peter, there, clerk, agent, collapse,

and in combination with other letters: break, beak, bread, idea, heart, bear; tee, beer; veil, neice, height, weight, heifer; their, weird; few, sew.