The FTB not really needed since we don't really have a wholesale passive fibre infra provider like in other countries.

For the FWS, in my opinion is more important to isolate and allow DIY repairs in future just in case the fibre cable is fracture inside your house and needs a patch cord replacement.

Usually the standard installation already provide the cable with a connector to be plugged directly into your modem. But my suggestion is go a little extra by asking the installer to plug it into the coupler and plug a patch cord to separate into 2 sections for easier future troubleshooting.

The coupler is to be inserted into the one of the slots in the FWS as a port.

Do check with your installer in advance which type of connector type they're using in your area before deciding to buy the correct coupler and patch cord.This is to avoid wasting your money.

I posted the parts list earlier is to serve as a benchmark or suggested retail price for most of the components for reference.

This is to avoid being cheated and overcharged by your local TM installers when quoting.

Your house is the apartment building in front? Looks like community flat.

That is a passive optical cabinet for Unifi FTTH. If VDSL2 cabinet got power supply unit next to the box.
Passive optical switching no need active power/electrical supply between OLT and customer premise's FWS.

Upto 800Mbps no problem