(Focus on regular options and ignore barrier option for now.)
Simple rule – in FX options,
– call-writing===writing-put. Not equities, index or commodity options though.
There’s never any equivalence between long vs short option positions. A short position (call or put) represents unlimited downside in FX. An experienced FX option trader once said option-writing is abhorrent.
After we get comfortable with these equivalence rules, then we can throw in PCP (put-call parity). Mixing PCP and the equivalence rule too early leads to brain-damage.