The first macro should be the best as it part of UE4 math library and it most directly define maximum value, but… this macros is used for something else which is TNumericLimits:
So you should use those insted, because if there something UE4 APIs then enigne and Epic expect you using it, it gives you guaranty that if there be any changes your code won’t feel it or at least you gonna be informed if change gonna happen by compiler warning if you updating UE4 regularly.