Based on the above (f) sounds best as it causes least stress in selling and buying.

Obtain loan on unencumbered unit.

Purchase your new PPOR with funds from the unit loan and top this up with a loan on the new property to complete the purchase. 

As your current PPOR is unencumbered this should really be a stressless process for you. It is much trickier when you have a fairly large debt already.

Many of the lenders have packages were this approach will cost you no more than taking out a single loan after settlement without the headache or even the necessity of finance clauses; thus placing you in a more powerful position to buy and sell at the optimal price.

Downside: until your unit sale settles, you will potentially need to service a larger debt for a few months. Assuming your income would service this additional debt – I would proceed down this path as it provides you with more options and peace of mind.

I hope this is helpful