I sent a few items to a friend in the US, who’s going to mail them together in one box via USPS. Most of these are supplements / vitamins, and will be over the $2,000 NTD customs limit. Also sending some mail and other personal stuff.
Will there be an issue at customs for receiving a personal package like this? Any tips or advice?
Expect to pay substantial (% wise) taxes on the value of your supplements and vitamins.
About the supplements/ vitamins
What if I have my friend take all the supplements out of the original packaging and put into ziploc bags? How would customs deal with this, if they opened the box?
I can also have them put in some other junk like clothes to make it appear like a personal items box? I read a post from someone that customs missed a laptop (in its original box) at the bottom of a box with personal items - does that work?
Do not do this. It is not worth the trouble. Really. For obvious reasons, customs finding ziploc bags full of unidentified tablets or powders in a package addressed to you is not something you want to have to deal with.
To the extent that what you’re importing is permitted to be imported, just pay the tariffs and be done with it.
You’re opening yourself up to a lot of questions, trouble, and potential fines. All your future shipments will be flagged for inspection as well.
This is great to know, thank you! So, should I have my friend include a printout with Amazon URLs and prices so they can calculate the customs tariffs? If it’s not in the box, how do they figure it out?
Thanks for all the great advice, @chydals, @RBE, and @jephhy! I appreciate it. 
When your friend sends the package, he’ll have to fill out forms disclosing what items are in the package and their value(s).
Boxes get x-rayed and picked out to inspect.