I suspect that it selects either usb-C or HDMI. I have heard that HP and dell only support the maximum number of monitors (3 for the L590) correctly with their own docking station. This could also be the case with Lenovo.
https://psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_L590/ThinkPad_L590_Spec.PDF
https://support.lenovo.com/de/en/solutions/pd029622
Yes, you can connect a USB-A mouse, a keyboard and a camera at the same time. The device is compatible with Mac as it was developed for Mac OS. It has two USB-A 3.0 ports that are suitable for such devices. Note, however, that the USB-A ports do not support Apple SuperDrive and cannot charge iPads.
The docking station is meant to be plugged directly into a device (laptop, tablet, etc.), it does not work via the screen.
As for resolution, USB-C has no video output, only HDMI supports up to 4K 60Hz.
You can find more detailed specifications at https://satechi.net/products/slim-aluminum-type-c-multi-port-adapter-v2?variant=12604200812632 and https://satechi.net/products/slim-multi-port-adapter-with-ethernet?variant=32219893891160. The main difference I noticed was the Gigabit Ethernet port on the ST-UCSMA3M item
I had the bug with the wireless mouse with various USB-C hubs, even with dedicated Thunderbolt 3 docking stations. The solution that worked for all of them was a USB extension cable that moved the receiver (Logi Unify for me) away from the hub. I read about this on some forum and I'm flabbergasted at how well it works.
I currently have a 2m extension cable (I didn't have another one) plugged into an Anker USB hub, which is plugged into one of the slots of the USB-C hub. The USB-C hub also has a power cable, HDMI and occasionally other USB devices. Never had any problems with delays, interruptions, etc. again.
It doesn't charge the notebook by itself. You can plug a charger into the usb C port of the Satechi like you would do by connecting the cable directly on the port of the notebook. It passes the power to the notebook up to 60W.
The best thing to do is to contact our customer service directly at https://helpcenter.digitec.ch/hc/de/requests/new. Your request can then be examined individually.