もしも～なら If, Supposing

もしも～なら and もしも～でも emphasize a hypothetical situation, similar to 'supposing that (A)' or 'even if (A)' in English. Separately, でも can attach to question words to mean 'any~', e.g. 誰でも 'anyone' and なんでも 'anything', or follow regular nouns to suggest a casual option, as in お茶でも飲みませんか？ ('Want some tea or something?').

なら is a conditional that follows phrases to mean 'if it's the case that (A)', often implying the condition is likely or assumed. もしも adds emphasis to the hypothetical nature of a situation and is placed at the beginning, e.g. もしも雨なら 'if it were to rain'. It can also appear with でも, e.g. もしも雨でも 'even if it rains' (implying 'I'll still go', etc.).

もし is typically used at the beginning of a sentence to emphasize that what follows is a hypothetical situation or condition, similar to the English 'if' or 'supposing that (A)'. もしも is a more emphatic version of this, and sentences with もしも almost always contain a conditional expression, as seen in the もしも～なら・もしも～でも pattern. The specific meaning is determined by the conditional, e.g. もしも～なら 'if (A)' vs. もしも～でも 'even if (A)'.

Both introduce hypothetical situations, but with different nuances. たとえ〜ても sets up contrast, like 'Even if (A), still (B)', e.g. たとえ負けても悔いはない 'Even if I lose, I'll have no regrets.' もしも～なら・～でも expresses a basic hypothetical and its result, e.g. もしも彼が来たら、話します 'If he comes, I'll talk to him.'

ても is a highly versatile structure meaning 'even if,' used widely in both speech and writing. In contrast, ようが～まいが is much more formal and mainly found in written or academic contexts. Both forms can express 'whether or not'. For example, 食べても食べなくても and 食べようが食べまいが both mean 'whether or not (you) eat', but the latter is more emphatic and formal.