大言壮語 is a more formal, four-character compound meaning 'boasting' or 'grandiose talk', while 怪気炎 is more colloquial and often implies flamboyant exaggeration.
ほら is a casual noun for 'boasting' or 'tall tale', similar in meaning but less formal than 怪気炎.
Etymology
Compound of 怪 (strange, suspicious) + 気炎 (spirit, fervor). The exact origin is uncertain, but it likely arose as a vivid expression for overblown rhetoric.
