I bought 2 cameras and connected them wirelessly to the Mercusys MB110 (4G / Wi-Fi Mobile Router) for occasional use at the cottage. I can confirm that their collaboration is flawless! Setting up the wireless connection is relatively easy, and I say relatively because while the first one connected seamlessly, the second initially "struggled"..., but in the end, it connected (I’m always talking about connecting to the router via WIFI).
This was the only negative (if it wasn't something completely random). However, what I noticed with this particular camera is that it cannot be rotated throughout its entire range via the app, but that’s not something that concerns me much since I can see what I want.
I did not encounter any disconnections from the wireless router or other problems at all, even though one camera is quite far from the router and many walls, corridors, and other obstacles are in between.

The mobile interface is very good and user-friendly.
I haven't checked all the features yet, only the basic ones, and I don't know if I will check them at all for the purpose I want, but overall, I am very satisfied.
The 4 stars are because in Athens, where I have a similar system with tp-link (but not on a Mobile Router), comparing the environment and usage via mobile/PC in cloud/apps, I find the latter much more user-friendly (although recently it has been disconnecting some cameras). If there wasn't the possibility of such a comparison, I would definitely give 5 stars, and when I upgrade my old system, I will choose the Hikvision solution since from comments I have read about the Tapo, they have changed quite a bit with their cloud and the subscriptions they impose.