Ok, so will be leaving my house in Italy for 8 weeks max and wondered if it is safe to leave the Max switched on with the chest freezer and my desktop pc (must be left on for various reasons) connected to the AC200max.
If I decide not to use the battery, should I unplug solar and switch it off completely with a full charge.
The answer is yes and no. If it has been working fine doing what you mentioned without any issues other than just monitoring it then you could make the decision to leave it running. If it requires some sort of action to keep running on your part then its likely it will still need that attention and could possible have a problem. I would hate to come home to a dead freezer of food after 8 weeks. I personally would split the difference and put the freezer on grid power (assuming the grid is more reliable) and leave the PC or something else running then if it made it the entire 8 weeks I would trust it for the next time. If you want to disconnect and walk away for 8 weeks then giving it a full charge and disconnecting is the safest way to go.
I would not do this. Not because of risk of fire but because nobody is there to attend the device if it goes into an error condition and turns off power.
Bluetti’s UPS functionality is not as reliable as a true corporate ICT UPS system. It may encounter an error and turn off or drain the battery, turn off and not turn on again. Just put the freezer to utility power. The freezer may turn off during a power outage but in Western Europe (Italy) chances are good that power is restored soon. Freezer will resume freezing and nothing happened to your food because a chest freezer can be without power for many hours without reaching dangerously high temperatures.
If the PC needs to stay on, I would use a PC/server UPS system for that. (It will protect only from short power outages due to limited battery capacity) if you do not want to buy that, leave the PC on via utility power as well.
Leaving any device on has a certain risk of fire but Bluetti has a lot of safety and quality measures built in to their power stations. These are reliable machines and I have no problem leaving my home with my Bluetti (AC300) on. Just don’t count on the UPS function to work unattended for a longer period of time to guarantee your connected devices to stay on.