@MikkieMikk 

If you ask this question, it means you don't care if you run Deco in Router mode or in Access Point mode. You have home network already and want to improve WiFi coverage with Deco mesh, nothing more.

That would be just like me when I evaluated Deco deployment, and I now run pair of M9 and one M5.

Let's start with two premises:

1. Wired is always better than wireless

As long as your wired network is gigabit (switches, cables), wiring devices with Ethernet cable is better than running them wireless. Even with WiFi 6 that holds true most of the time, but with WiFi 2.4GHz and 5GHz it is true all the time. Deco M9 do not support WiFi6.

2. With any networking equipment, less functionality overhead means better performance

It is also KISS principle: if you don't need feature, don't utilize it. Just read this forum on topics of QoS and how improperly setting it severely limits Deco mesh performance. No QoS in Access Point mode, no potential headaches. If you don't care about Router mode vs. Access Point mode, go Access Point.

If you agree with these two, the answer on your question becomes obvious: Option 2. Wire everything you can and run Deco mesh in AP mode. 

@Alexandre. Thanks for your reply!

Actually that is my question. How good is the router function compared to the router of my provider with adapted provider software.

Is it a shame to turn off the Deco's router function or does it not matter in terms of performance?

normally I always put the modem in bridge mode so I can use own router. But against that I don't use specific router functions.

What is the best way to do it

Old setup

Modem in bridge --> apple time capsule/router --> a couple devices wired.

Want more wired connections and better wifi.

@MikkieMikk 

I run my Deco mesh in Access Point mode since I bought Deco M9/M5. I have configured my network to my liking before I deployed mesh, but was not happy with WiFi signal.

I prefer to follow KISS principle when making changes: if I like what I have, I keep it, and only replace what doesn't work.

So, can't tell you how good or not Deco router functionality is, but I have no complains when running Deco mesh in access point mode.