I need advice

Low frequency ( LF )  transformer based inverters have advantages over high frequency ( HF ) transformerless in that they are able to support higher  surges in load current for longer durations, this is particularly important if motor loads are to be powered. Transformers are more reliable than the MOSFET's used in high frequency switching especially at higher power but do add to the overall mass and footprint of a given rated unit.

Price wise HF are less expensive but are not well suited to industrial type loads, so it really depends on load type and or budget, the better choice in my opinion are LF types if you can afford it, others may have differing opinions.

https://www.magnum-dimensions.com/knowledge/high-vs-low-frequency-inverters/inversion-methods-explained-high-frequency-vs-low

The idle consumption has little to do with the type of inverter but rather with  the individual manufacturer, getting the actual amount from the specifications before purchasing is important, some have a energy conserving search feature which wakes up the inverter when a load greater than the preset value is present. It must be noted that some smaller loads such as LED lights may be insufficient to activate the feature.

All types must use some amount of energy to be in standby, a tare load of 20W or less would be in the good category, the Cloud website has no information on the amount it uses, the specifications prompt reveals nothing, I would contact them directly to get the information.