Your first sentence is an example of what is sometimes taught to foreign learners as the Second Conditional, which envisages an unreal, unlikely or imagined situation. In these sentences, the verb in the if-clause is in the past tense. The verb phrase in the main clause is usually made up of would followed by the plain form of the main verb, but other modals such as could are also found.
Your second sentence is an example of the First Conditional, which predicts a likely result in the future if the condition is fulfilled. Its typical structure is present tense in the if-clause and will (or won’t) in the main clause, but can is also possible.
The term 'conditional subjunctive' is not normally used.
You're confusing traditional Latin grammar terminology with English grammar terminology,
and with modern linguistic terminology, as well.
Mood, Voice, and Tense were traditional inflectional categories of Latin verbs. I.e,
every verb in Latin was inflected (marked uniquely) for some mix of mood, voice, and tense.
Latin had six tenses (by a strange coincidence the same six you listed),
four moods (indicative, subjunctive, imperative, and interrogative),
and two voices (active and passive). That was Latin.
English has two tenses (Present and Past), no moods, and no voices.
In particular, English has no subjunctive mood, so you don't have to worry about it any more.
However, many other languages have rich inflectional systems, even richer than Latin.
Sanskrit and Greek both had a Middle Voice as well as Active and Passive, for instance,
and an Optative Mood (used for things one wishes and hopes for), and Sanskrit also had a Benedictive Mood (used for blessings).
And that's just Indo-European. There are lots of other ways to organize these matters.
Best Answer
This usage at one point existed in English but now mostly survives in fossilized phrases like "be that as it may" or "if need be." So I think you are not incorrect to say that if you are specifically aiming to write archaic English it is not wrong to use.
But to the second part of your question, yes, I do think this is likely to be mistaken for the imperative, because many, if not most, people are not familiar with this construction outside of the fossilized examples. You will have to judge how erudite your readership is before deciding whether to risk that.