Which formulas support characters like the "&" "|" " * "

How would I check which formulas support characters like &,|, and *?

This source lists all but "&" as REGEX characters. https://support.google.com/analytics/answer/1034324?hl=en&ref_topic=1034375

Does this mean that they are only usable in REGEX formulas? (R.-MATCH -EXTRACT -REPLACE) and QUERY? Is the & sign only applicable then, in patching text together like this - A1&"whatever" -?

I could not find a definitive source for this topic, can you help me out? :)

(I'm asking because this is clearly not working while being the more clear solution: IF(A1=1 | 2, TRUE) and needs to be done redundantly like this IFS(A1=1; TRUE; A1=2; TRUE) )