って

って is the casual spoken contraction of という／とのことだ, freely dropping だ (来くるって). と言いう is the neutral choice, equally at home in writing, and never drops だ.

そうだ has its own polite step (そうだ→そうです, still hearsay). って has none, more formality means switching to という／とのことだ.

って strips the relay down for speech, dropping both 言いう and ている (来くるって). と言いっていた keeps the verb, letting a subject and topic go with it (田中たなかさんは…と言いっていた).

って is と言いう relaxed for speech, dropping 言いう entirely (来くるって). と言いう stays for a written report or a record of who said what.

って lives in speech only, taking the bare noun or だ alike (中止ちゅうしって／中止ちゅうしだって). とのことだ has no casual use, fitting only a business email or memo.

って is the spoken stand-in for this と, and drops the だ that と keeps (雨あめだと言いった／雨あめだって言いってた). と is what writing uses instead, a printed article never reaches for って.

って commits you to having actually heard it said (結婚けっこんするって). とか keeps the source vague on purpose, letting you back out of it.