The wording of the questions seems to indicate an oversimplified view of things. Hope this helps clarify.
1) PV's produce a voltage potential when exposed to light. If connected to a load, current flow. If not connected no current can flow. As far as I know there is little or no correlation to panel aging and degradation based on whether the panel is connected to something while voltage is present.
2) PV Setup is a broad description. A solar system consists of PV's, wiring, inverters, microinverters, AC chargers, charge controllers, batteries etc. Lithium Iron Phosphate which is used for stationary storage is MUCH safer than Li ion types like LiNMC used in automotive applications due to its higher energy density. Other components like electronics or wiring can and do overheat and cause fires. This is why properly sized fuses or breakers are used. Statistically speaking, I don't know if there is a greater or lesser chance of experiencing a fire as compared to homes or vehicles without solar.
3) Alibaba is both a good and potentially bad source for purchasing solar components or generators or any other item for that matter. Yes, its best to avoid Cheapass products with prices that are "too good to be true". On the other hand with a bit of research and upon establishing a good relationship with an Alibaba supplier via email, you can save money on products that will meet your expectations.
