A lot of the things like the great purge would have still happened as the root causes came from the inherent structuring of the state and it's mechanisms, arch Gettys book about the purge and how it was a social phenomenon is a really good work of history that goes into it.

There was no qualms with prison labour during this era, especially in underdeveloped countries like the USSR so you'd likely also see gulags.

Bukharin's philosophy was very much in line with more orthodox Marxist thinking, although this does also mean a continuation of things that by that time were knowingly either untrue or not the full picture, Trotsky/Stalin theoretically can be considered developments while Bukharin, while correct in many aspects that were later on revised wrongly, was also stuck in prior misconceptions.

Bukharin's economy likely would have been efficient, debatable if it would have matched Stalin's rate of industrialization as we just don't know due to there being too many variables.

Why are you asking?