Help finding right documentation on how to handle carts and wishlists

Hi,

Well, I don't know of any central documentation where you would find all that.
One thing is sure is that the first thing to do is to turn off all the caching of the website (the Joomla configuration cache, the system cache plugin, 3rd party caching extensions etc) and see if that helps.
Another thing to test is to switch to the default template of Joomla and see if that helps.
Most of the problems regarding to the cart/wishlist are linked to either one of these.
Besides that, we would need precise information on the problems you have to reproduce, analyze them, etc to be able to say more on the subject.

Hi,

Not necessarily.
For example, HikaShop should work fine with the normal caching system of Joomla as we added some code to HikaShop in order to clear the Joomla cache when the cart is modified or when you change the current currency.
But some third party cache extensions might not play nice with HikaShop based on how you configure HikaShop and the cache system.
So if you have some refresh issues with the cart system, the first thing to try is to turn off the caching system(s) you have and see if that helps in order the understand if the problem comes from that or something else. Then, you can see if you can configure it to avoid conflicts or use another one which works better or configure HikaShop differently to avoid the problem.

Having thousands of products or only a handful of products shouldn't change much with or without cache. It starts to get useful when you have have several tens of thousands of products.