Default rule
Use what the device page or manufacturer names. If the maker says alkaline only, do not substitute NiMH. If they allow NiMH or “rechargeable”, NiMH AA/AAA are usually the intended chemistry.
Why devices differ
Alkaline starts near 1.5 V per cell; NiMH sits near 1.2 V. Some remotes, clocks and sensors brown out or behave oddly on NiMH even when the cells fit.
Lithium primary AA (e.g. L91) is a third chemistry — Nest Protect and some cameras specify it. That is not NiMH.
Remotes and low-drain gear
Many streaming remotes accept alkaline or NiMH. Soundbar and life-safety devices often ban rechargeables — follow the device caveats.
Charging
Only charge NiMH (or other chemistries the charger supports). Never put alkaline cells in a charger.