Welcome to SNB!
For FPS gaming, the most significant things you want to do networking-wise are 1) hard-wire your gaming PC (never game seriously over wireless) and 2) ensure you have proper QoS in place, if required, to eliminate
bufferbloat (which is often the primary cause of most network-based gaming issues on residential networks).
#1 is fairly simple. Just make sure you have a good quality patch cable from your PC to your router, plus the most up-to-date/stable drivers for your PC's network card and chipset.
#2 can be a bit more technical. The simplest option is to just see if the ISP combo unit will perform well enough on its own, with routing and wifi included. With your PC hard-wired to the Technicolor, head over to
DSLReports.com/speedtest and perform a test.
If your bufferbloat score is an A- to A+, you'll probably be fine using the Technicolor as the router, or you could use any of the routers you listed with the Technicolor in bridge mode. If you went with your own router, for simplicity and reliability I would lean towards an Asus running
Merlin.
If your bufferbloat score is a B+ or much below that, you're going to want a router that offers
SQM QoS, in combination with the Technicolor running in bridge mode. For SQM to be applied properly, you will want a
Qualcomm-based router (no Asus models; they're all Broadcom-based). I could get into the technical explanation of why that is if desired, but suffice it to say, just trust me. The simplest option for that would be an
Eero Pro base unit; just install via the wizard, turn on "SQM" in the Eero Labs section of the phone app and you're done. If Eero is not available in Portugal, then the next best option would be
OpenWRT installed on a Netgear R7800. Configuring SQM on OpenWRT is a bit more involved, but not too bad with help from Google and OpenWRT's forums.
The above approach should maximize your gaming performance for Call of Duty.