hypothetically speaking vs theoretically speaking “hypothetically speaking” would be "if X were true what would it mean for Y” e g “hypothetically speaking, if the sun were a binary star what would it mean for Earth” While “theoretically speaking” means it is possible in theory but not necessarily in practice
Hypothetically speaking - English Language Usage Stack Exchange hypothetically adverb By imagining a possibility rather than reality; as a hypothesis - Lexico At the immediate level, the preface of "hypothetically speaking" marks the communication as merely theoretical, not real However, just because someone calls something hypothetical doesn't make it so
word choice - English Language Usage Stack Exchange Stack Exchange Network Stack Exchange network consists of 183 Q A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers
modal verbs - English Language Usage Stack Exchange Used hypothetically, could and might are substitutes for may in expressing factual possibility (see §121): There could be trouble at the World Cup match tomorrow | The door might be locked already | Our team might still win the race
Supposing, Let us suppose: differences in hypothetical sentences In the context of your specific sentences, I think both constructions are equivalent Let us suppose is a construction that I would expect to hear in the context of a logical argument or a mathematical proof where an initial assumption is made for the sake of the argument, especially when the point is to prove the assumption is true
auxiliary verbs - English Language Usage Stack Exchange Stack Exchange Network Stack Exchange network consists of 183 Q A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers