Aleternative Network Architectures for Zerotier

It seems there are 2 different ways I could setup ZeroTier to enable access beween and to 2 networks.

I have 2 home networks in different countries,
say Timbuktoo and Babylon, both with fixed ips.
I would like to be access devices (eg IPCams) in both networks
from outside (eg mobile phones) and from linux laptops in the other network.
The laptops may move from one network to the other.

Both networks have a main Openwrt-type external-facing router
with subrouters under it at addresses,

At the moment all devices are reached from the outside by fixedip:port number.
or from the inside by lanip:port number.

Method 1: Two Zerotier networks.
I set up two Zerotier networks.
I install Zerotier on the main external-facing routers and on the mobile phones.

When I want to acces a device on (say) the Timbuktoo network from a roaming mobile phone
or from a laptop inside the Babylon network
I address it via its ZeroTier nework address and port number.

Possible Problem:
It seems mobile devices can connect to only 1 zerotier network at a time,
so could not access IP Cams in both networks without disconnecting/reconnecting.
So the IPCam monitoring function of the mobile hone app would fail.

Method 2: Single Zerotier network
I set up only one Zerotier network.
Make both Timbuktoo and Bablylon part of this Zerotier network
I install Zerotier on the main external-facing routers and on the mobile phones.

( I would have to change the lan address of one of the main networks from to (say) to avoid ambiguity.
The inner netwrks, dont need to change. )

In Both Architectures
I do not need any “managed routes” or fixed routes.
I do not need to install Zerotier on the laptops as they are always behind one of the 2 routers.

Sanity Defence
Is the above understanding correct?
I would be grateful for any comments or disputes
as I would like to understand what I am doing before I do it.