Which telecommunications home connections are sensible?

Stand on your property with your smartphone. If the device shows 4G or even 5G, you can safely forget about the copper cable. At Congstar, there is a Homespot with 200GB for 40 EUR/month in 5G. This almost fetishistic fixation on cables is quite interesting. Mobile communications and Wi-Fi don't even come to many people's minds... yet by now, they are more powerful at many, many locations than the copper cable in the ground...

As a backup, I would also rather advocate for a mobile router. We used something from Megasim as a stopgap, which was €20 per month for truly unlimited volume at 10/5Mbps and - very importantly - cancellable on a monthly basis.

Stand on your property with your smartphone. If the device shows 4G or even 5G, you can forget about the copper cable.
At Congstar, there's the Homespot with 200GB for 40 EUR/month in 5G.

This almost fetishistic fixation on cables is quite interesting.

Mobile communication and WLAN don't even cross many people's minds... yet by now these are more powerful at many, many locations than the copper cable in the ground...

We have been working exclusively via mobile routers for almost a year. The problem is not the speed. The problems are the ping (completely unsuitable for gaming) and reliability. The cell tower (by the way, the same one that also covers the new property) has completely failed 3 or 4 times within less than a year. Sometimes it lasted a few hours, sometimes a few days, and once almost 2 weeks straight. No network, no phone, no internet. That can't work in the long run if 2 people are supposed to work remotely.
And in the evenings, I also don’t want to constantly tell my husband "turn off the video, I need to switch to hitscan." That’s just crap.

I have 2 kids, a job, and a new building with lots of self-work... so I rarely game, please forgive me for that.

But even if I did, I would probably be way too stingy to put 800 rogues plus peripherals on the table just to play a few months without Counterstrike, WoW, Fortnite, or whatever people "game" today...

The outages... annoying, I know. But that doesn't have to be a rule. I have never had no internet for more than 2 hours... and I am a field worker, I travel a lot.

I'm happy for you, but unfortunately that does not apply to our network coverage and outage situation.

Furthermore, we like to neglect our sleeping children for a long and extensive time to indulge in wild gaming, so please accept my apologies for that as well. :D

In our new development area, fiber optic is being installed, which could roughly coincide with the move-in time. We have already signed the contract with Toni (BBV) for €600 for the house connection + €100 activation fee. Are we thus well equipped for telephone, internet, and TV?

Or should we still apply for an old-fashioned Telekom copper connection for about €800?

If this is a completely new development area, there will originally be no copper connections anymore. What Telekom then offers as so-called copper is more likely a fiber optic connection (as a reseller, if they are not the fiber optic provider themselves!) which is converted to copper technology, and is therefore more susceptible to interference than pure fiber optic.

We inquired about a cable connection with Vodafone but received a rejection for our area, although the city had marked the cable connection as possible when selling the building plot.

The city has no influence on which network operator throws their hat in the ring with the Federal Network Agency first. If Vodafone knows a competitor supplies with fiber optic, they will not even connect the development area—because then they also know they would have to rent the competitor’s lines or would only be allowed to install copper "next to it." And that makes no sense, because at today’s prices no customer will buy half the speed for ten euros less per month. They practically all offer triple play nowadays.