A few points to respond:
Visonic have some really strict rules about country compatibility, and buying one that is unofficial can make buying accessories quite difficult (e.g. Some sellers on eBay will be flogging a non-uk version as it could be cheaper to buy for them, and it will be get hard to buy extra sensors). Hence I’d suggest you send me the Amazon link to confirm it comes from a good seller rather than a noname unofficial third party seller.
I bought an Express E system from the uk to test (from SapphireSecurity) and it worked for me, but took some time to enroll, however I am aware of one user with a Dutch Express version which doesn’t work and I don’t yet know why. The other people with problems are Powermax Pro in the USA I think. Put simply if it’s an official version then you’ll be fine I’m sure. Complete is another option which works very reliably, and they have basically the same features (complete has more features but they are fairly redundant now compared to when it was first released), but don’t know how pricing compares (I bought my complete from MAP security and they were one of the lower prices, but there are plenty of sellers out there).
Phone line functionality is fairly useless with this integration since you can do the same and so much more with Wemos and Wi-Fi. The Wemos works like an internet module instead of the GSM module hence they are totally separate. Imho, GSM is only useful if you are worried somebody is going to cut your internet connection (but if worried about that then you probably need a better alarm system).
As for the Wemos I ship first class and normally within a day or so depending on my work, so pretty quick.