How do I get WiFi and phone service, technology in the basement

phew with ThermoMix it naturally gets tight.

Jokes aside. Yes, that is more than enough. You’re not even remotely pushing the cat7 to its limits. If you use a Fritzbox, you should also use the matching Fritzbox repeater/access point (for example FritzRepeater 2400) because then you only broadcast one Wi-Fi for the whole house and prevent switching back and forth between different Wi-Fis.

No repeaters. If using Fritz APs, then operate them as real access points connected by cable.

How many floors do you have? I only read something about the basement and the ground floor.

I would first try to use only one Fritzbox in the basement for the phones. The signal passes through walls and ceilings better than WLAN, maybe that's already enough to make calls throughout the house. For WLAN, of course, one access point per floor.

If you are not very demanding network-wise, the Fritzbox on the ground floor without access points could also be enough. As with the phone: just try it out. You can always switch and expand everything in the basement later.

Cat 6a is more than enough. Cat 7 sockets would be a bit over the top. The current standard for data up to 1000 Mbps is Cat5e (100 MHz).

I would just try it. We always lay duplex, so one port can be used as a feed for DSL/fiber. And the other port can power a switch in the distribution panel. The phone can be connected either via A/B port or DECT to the Fritzbox. And then see how far you get. I use a 7590 as a router and a 7490 as a router. One is enough to cover the whole house.

When is the move-in planned? I would currently delay the device selection as long as possible, since WLAN is currently switching to WIFI6. Since you are practically dependent on WLAN, I would try to go with WIFI6. It is important that you stick to one manufacturer and possibly also one series. If you are already talking about the FritzBox, then everything from AVM. The 75xx AX was announced briefly, but AVM retreated after participating in the virtual IFA. I think AVM now wants to first introduce the new FritzOS on the current devices.

Whether WLAN is sufficient for you also depends on your requirements. Stable WLAN is generally slower, and fast WLAN less stable. Additionally, there are other influencing factors with WLAN. One of these can be the WLAN networks of your neighbors. Usually no big problem in a single-family house, but in a semi-detached or multi-family house this can be a challenge. Another point is the structural conditions. How many walls must the signal pass through, what materials were used, ... Your WLAN device (router or access point) should be placed as high and free as possible. Please do not put the devices in a cabinet, on the floor, or directly next to other electrical devices.

Sorry if I step in here briefly, but I have to ask something quickly.

If you use a Fritzbox, you should also use the matching Fritzbox repeater/access point

It is important that you stick to one manufacturer and possibly also one series.

My plan was actually to combine Fritzbox as a modem with Unifi lite access point(s), phone also via Fritz.
Will I have problems because of the different manufacturers?