Hi folks, some advice on switching ISP and transposing existing deco set-up please.

I have 3 x Deco S4's currently set-up in router mode with a Virgin Media Router in bridge mode. One of the sateliites has ethernet backhaul.  I am switching soon to Vodafone Full Fibre 910Mb (FTTP).

At first I had researched that is should be possible to ditch the VF router and use the deco S4 directly connected to the ONT (firstly obtaining credentials from VF) but Ive seen several posts where this didnt work or was difficult to get working (something about Mac cloning was a solution for one user) and when future trouble shooting with VF should occur, I'd need the VF router connected up again. I'm not all that techie when it comes to networking.

Therefore, I had figured it would be more starightforward to keep the VF router in situ (THG3000 cannot be set to bridge mode apparently) and change the Decos to operate in AP mode. Most of my devices around the home are connected via ethernet but wifi speed is still important too.

So couple of querries:

1) why is it recommended to turn off the wifi on the VF router when deco in AP mode, is it just intereference concern if the main deco and Vf router are close via a short ethernet cable. Would it help if I used say a 5M ethernet and moved the 1st deco further away in the same room?

2) In AP mode does the SSID of the VF router, just get replicated by the deco or would I have two SSID's (e.g. SSID=Vodafone 123 and Deco wifi123). I would only want one SSID so if both SSID's would exist, I would be pushed towards turning off wifi on the VF router anyway.

3) Am I losing any max speed via the deco S4 compared to the VF router ( Im guessing no with ethernet but maybe a little with AC1200 wifi)?

4) Would you start from scratch setting up the deco's in this way (not sure how to start fresh) or can I just switch the Decos off make the connections to VF router, switch deco back on and change over to AP mode?

Lastly, anyone have experiance of port forwarding with the THG3000. I currently have this set-up on my Deco so that CCTV DVR can be accessed when away from home.?

Thanks in advance.