What are some of the key factors that determine the optimal balance of processing power, storage capacity, and battery life in modern computers and mobile devices, and how can users make informed decisions about which devices and components to choose based on their specific needs and preferences?
There is no such thing as a single right answer when it comes to this topic. Every person's usage pattern, budget and requirements will differ so there won't be one-size fits all solution. However here is a few pointers:

Decide what your priority list would look like before buying anything (i.e., RAM speed, Storage space vs battery time) - prioritizing them will help you figure out which components are worth investing in or if you need any add ons. 

Opt for products with ample upgrade potential - upgrading components usually takes more time than purchasing a new unit. Therefore opting for systems that allow upgrades over multiple generations could save money at first but require less frequent upgrades later on.

Get good value from the component - often cheaper versions might not provide comparable performance while costing way more per GB compared to similar quality products available on ebay or aliexpress. Check for reputable retailers/vendors rather than unregulated online stores to ensure safety.