Would more likely & would most likely

Using 'likely' in this way is mainly American:

AmE: I would likely faint if I saw blood.
BrE: I would be likely to faint if I saw blood.

Having got that out of the way, we use the comparative 'more' and the superlative 'most' conventionally: use 'more likely' to indicate which of two alternatives or choices is preferable or likely; use 'most likely' when there are three or more choices.

I would more likely run than fight* if a robber attacked me.
I would most likely choose cavatappi** for a simple pasta dish.

* Two alternatives here.
** There are more than two possibilities.