I am also an HKS fanboy, however, common sense also prevails.
I see no real benefit in using an HKS oil filter over a Genuine Stock Nissan OEM oil filter at half the price of HKS.
Also HKS do not make there own oil and it will simply be some other stuff rebranded.
Another disappointing previous example was that HKS were selling "HKS" braided brake lines which turned to be simply HEL lines which were rebranded HKS, sad days I am afraid.
Most HKS products are top notch, however, above are a few examples which have dropped through the cracks.
Like most top branded products if you go the HKS route then you will have to pay the HKS tax.
Regarding the oil viscosity, top branded 5W 40 will be fine for your 86k 350Z.