The difference between the Unicode characters U+02C1 ⟨ˁ⟩ and U+02E4 ⟨ˤ⟩ is not well defined.
U+02C1 (modifier reversed glottal stop) is given as a typographic alternate of the Egyptological ayin, U+02BF ⟨ꜥ⟩, which would be transcribed in IPA with the letter U+0295 ⟨ʕ⟩.
U+02E4 (modifier small reversed glottal stop) is defined as a superscript IPA letter U+0295 ⟨ʕ⟩,[1] and the IPA identifies it as the character for pharyngealization.[2] The 'small' in the name (normally meaning 'lower-case' in Unicode) is misleading, as the letter ⟨ʕ⟩ is unicase.
U+02C1 may be set as a dotless reversed question mark ⸮, contrasting with 02E4 set as a superscript ⟨ʕ⟩. However, depending on the typeface, there may be no graphic difference between 02C1 and 02E4.