The word efficienct is often mis-used in vanworld to mean something like:

• better
• makes more power

… both without describing the use case.

It will simplify matters if we think of efficiency as power in / power out. Round numbers example: if a component requires 220W in to make 200W out then it is ~90% efficient with ~10% lost, typically as heat.

Made up examples:

• 200w inverter, 90% efficient
• 1000w inverter, 80% efficient

Which one can make more 120v power? The 1000w one. Which one is more efficient? The 200w one.

Solar panel efficiency doesn't mean how much power the panel will make or anything like that. A more efficient panel and a less efficient panel of the same rated wattage will harvest the same power, all other things being equal.

Panel efficiency is a mathematical relationship between the panel's area and its rated power. Efficiency makes no difference unless you are maxxed out for panel space.

MPPT are not more efficient than PWM controllers. MPPT have DC-DC conversion losses (typically ~5%) and PWM do not.

Will the MPPT harvest more in Bulk? Yes, on average MPPT controllers will harvest ~13% more energy (Watt-hours) from sunlight than the same system on PWM. But it incurs losses while doing so. There are scenarios where PWM can harvest more power than MPPT because of MPPT's buck/boost losses.

Inverters are the usual case where efficiency is discussed accurately; see the examples at top. Even then we often do not account for standby losses.