Generally i would think most heat-generating appliances (microwave, stove, hot water) are the elephant in the room, energy-wise.
One of the best things people can do to save money from energy consumption is optimise how they use the high-power devices -- swap your conventional oven for an air fryer, for example. Trying to optimise the smaller items, as we all here know, rarely returns the investment of time and (human) energy.
For the energy consumed the voltage is close to irrelevant.
A 26 A cable and appliance?
I do wish panel-level monitoring was cheaper, though; does anyone have any suggestions for this?
There's this forum thread on Tweakers.net (Dutch): https://gathering.tweakers.net/forum/list_messages/1578510
There are also plug-and-play devices like https://www.homewizard.com/
Other than that, I think the meter types and data standards differ somewhat between countries, so it's probably best to research how it works in your own country/area.
If you live in a net heating environment then the cost of running something like a toaster is basically zero. You're getting to cook with and getting the heat in the inside of your home as well. Not as great as a heat pump, but there is a reason why heat pump toasters don't exist.
I'd imagine most people run an extractor fan in their kitchen to get rid of smoke, aerosolised oils, etc. in which case almost all of that heat's lost.
Another option is an anti-backdraft cowl and some insect mesh... if you have an air quality monitor take a look some time at what happens to the air quality in your kitchen when cooking (especially frying) - it generally takes quite a dive, particularly if you have a gas cooker.