Network construction office next to residential building?

I moved into a house wall by wall next to my office. The question now is how to build the network most skillfully. Since the Internet line in the office is absolutely sufficient, a DSL connection can be used for both.

I tend to use between 1. Guest access of the Fritzbox and use additional repeater or take 2 Old router and build their own network and pull Internet from the Fritzbox.

Background: In the office I already have 5-8 PCs / laptops plus mobile phones / tablets again. At home, I have Google Home / Philips Hue, which should not necessarily be able to control the employees.

Option 1 I would prefer, because less work. However, I wonder how many devices such a Fritzbox can easily manage? In both networks, I come across 4 repeaters, 9 PCs / laptops, 8 tablets, 8 phones and 15 Google Home devices. Does the little box do that at all?

Variant 1 with repeater. Although we have only (!) 18 devices connected to it, but absolutely no restrictions. I think that other devices should not be a problem either.

Since the Internet line in the office is absolutely sufficient, a DSL connection can be used for both.

Can you do that? But tax is problematic, because in a mixed use you have to split the costs of telephony / Internet proportionally in the Fibu. And what does "sufficient" mean?

Background: In the office I already have 5-8 PCs / laptops plus mobile phones / tablets again.

Then a conventional DSL connection is certainly not enough. VDSL50 already rather, but even there it is when streaming parallel to the work already if necessary. Eng.

In addition, the home network must be physically and logically separated from the corporate network, for example, by a second router. This is not only necessary to secure your own data, but also to segment and backup the data that exists in the company network.

A separate VDSL (better cable) access for the house is therefore very advisable - which also has the charm, in case of emergency, if necessary. Per LAN cable times quickly keep the company network online, so that the employees remain able to work (quasi backup uplink ).

Addendum: The drilling of the outer walls for the purpose of producing a cable connection is incidentally inadmissible, and in addition even prohibited by fire protection.

Thanks for the detailed answer.

We have a 100Mbit line and almost all business PDFs, or encrypted data in text format, so relatively small amounts of data. There are still 3-4 people watching movies without noticing something.

Tax separation I get. In addition, in the house is also my "private" office space, so I have to divide either way.

We have no data in the network, we use a cloud solution. And the data on the PC's / laptops are, the networks also "change" as soon as someone works at home / on the move.

Fallback we have over LTE, so here is no need for a second network.

Therefore, the initial question remains whether it makes more sense to use the guest network as a separate network or if a router needs to be. Purely of network stability / problems with multiple repeaters or a router as an access point.

A hardwired solution would actually be the better choice. But this is also about the guest access the fritzbox. Via the interface number 4.