Simply search for food coloring pens. Patisserie shops sell them, and so does Amazon, but I wouldn’t draw on a kid’s banana with a random pen ordered off of Amazon, unless it’s a reputable brand.

I’d probably set up some firewall rules / a VLAN to isolate the cameras. I generally don’t trust any company to do the reasonable thing, and apparently, these days, we live in a world where many companies are outright malicious.

You can trust them about this much:

https://www.theverge.com/23573362/anker-eufy-security-camera-answers-encryption

All while constantly scratching your butt due to the worms. Ah, Rome.

As others have said, there is an “HD” button in the upper right corner which does what you want. It is always there, even if the background of the image obscures it.

There is also an option in “Advanced–>Media” that makes this behavior the default. You can also check if the data saver options for mobile and wifi are enabled.