I've just registered Unifi with TM, the technicians will be coming to setup by later this month, but I'm kinda panic after I ordered Unifi.

I'm a SoHo, having 3 computers, 2 network printers and 2 NAS in my home working environment, there are also a lot of P&C data in my storage, it MUST NOT be accessible by others. I'm quite panic about the Unifi security issue posted everywhere in the internet. I hope someone can give me a helping hand or suggestion on the following issues:

1. Security
Is it safe enough I just disable the the 'Remote Management' and change the password for both 'admin' and 'operator' account? Can this block TM or attackers by 'easily accessing' to my router? If NO, please tell me what else can I do to make myself protected.
2. Custom Router / Switch
i. Currently I'm using a Switch to connect all my office PCs, printers and also NAS, but in Unifi site, I saw the line: "...is only compatible with computers that are wireless enabled...". I then google online and I found The Unifi Handbook - Using Custom Routers, by following the steps provided, we could actually make the TMnet Dlink DIR-615 G1 as a VLAN bridge. If that so, I wonder can I setup my network like this? 'Fiberhome (VDSL) --> Dlink DIR-615 G1 (VLAN bridge) --> My Router --> My Switch --> PCs, network printers, and NAS (with network cables). Is this possible?

ii. Is it encouraged to do a 'custom router' setup? Will this setup slow down the network speed (or slow down when it's using network cable)??
3. IPTV
If the 'Security' and 'Custom Router / Switch' are successfully applied. Will I lost my IPTV service???