Amcrest is essentially the US-branded Foscam brand. They do not have the firmware issues the Foscam branded cameras have, and have been updating their product line pretty fast. I’d recommend them, and highly recommend using Power over Ethernet (POE) models. I have almost all wireless, and they are nothing but problems unless they are really close. The POE models I have give me uninterrupted 20FPS as their peak resolution.
Regarding security, I highly recommend putting all the cameras, POE or otherwise, on their own secured networks. Then use Blue Iris or other programs to access that network via a VPN or similar secure connection. The goal should always be to isolate the camera’s access to the internet.
I have a couple D-Link DCS-2630L cameras as well. While they are wifi only, the 180 degree FOV is amazing. I highly recommend wide FOV cameras over the pan-tilt style, because you don’t have to set up any scanning profile or set up methods to have the camera pan to the motion area, etc. Just cover the whole area with a wide FOV and you won’t miss anything ever.
There are some programs out there that will work, webcams on computers as well (Blue Iris will work with webcams). I haven’t tried using old smartphones, but remember it’d have to stay active always (and plugged in too), just like other cameras. But there are apps for phones that will stream the video, you can probably get Blue Iris to read the stream from the app.