Best used mirrorless for $300-$400?
Mostly for travel, social events, portraits
>Used Fuji X-E1 /Sony NEX-6
These are cameras of the OM-D EM5 era which depreciated a lot but are still pretty good and have a lot of features. Try get a X-E1 18-55mm lens combo to get that god tier kit lens.
X-E1 or X-Pro1 Are pretty good options for the price. X-E1 at least has a semi decent focus peek setting for manual lenses too if you're too poor for more of the beautiful XF glass.
If you have a lot of legacy EF glass then you can probably pick up an EOS M/M3 for pretty cheap too.