The LH A346 F is still an excellent product and will be miles better than what Q suites offer. That’s not to say that the Q suites are bad, just that Q suites are an excellent business class. LH F, despite its age, is still an excellent first class. The only real point of obsolescence is the small TV screen, which shouldn’t matter since it’s a night flight.
I personally prefer the second row in the A346 because it makes the cabin feel more spacious, but this is subjective.
In FRA, not sure what gate you will arrive at, but it’s probably best to go to the closest FCL. If arriving at Z, that means FCL A. If B, FCL B. TXL will likely leave from the A gates which means that if she goes to FCL B she will he driven to the plane. If FCL A, she will need to go to the gate on her own.
Some here advocate for going to the FCT. This would involve going through passport control, leaving the airport and walking outside. Depending on the weather and how tired your wife feels, this might not be a pleasant experience. The only advantage the FCT offers compared to FCL A is that she will be driven to the plane no matter what.
Some people care about that, others don’t. I’m personally a bit divided. If the weather is nice, and I have a not-short connection and I’m not tired, I would be inclined to go to the FCT. If the weather isn’t nice or I’m tired, I wouldn’t be bothered to go.