Parallelism in clauses?

Parallelism is a grammatical option to make sentences easier to read by making sentence parts more similar to each other, like "I cooked it, I prepared it, and I ate it," as opposed to "I cooked, prepared, ate it." (The removal of the final "and" could imply some rhetorical form, but admittedly this sentence is more hard to follow.) Bottom line, parallelism is optional, and is not necessarily something that is required in most cases, though it is often employed to provide understanding. You do not need to utilize parallelism if the ideas you are presenting can not be easily brought together (unlike a simple order of actions like I presented earlier, the most common usage of parallelism), like, for example, different tenses.

I would like to point out that your second sentence sounds a bit unnatural, and might not need to use parallelism, since the ideas you are presenting are rather contrasting, and do not need to be made similar to each other syntax-wise.

Perhaps you could employ parallelism to verbs with different verb tenses, but this is often not the case, as the verbs need to be changed to match the tense; parallelism is mainly for actions in one tense.