Subframe connectors for a driver/cruiser, necessary to weld to floor?

I put them in every car I build bc they do stiffen the car up considerably and do make the car handle better. I cannot say they would make a car launch harder bc I don't have any direct experience with that, but in "theory" I would think they might as they would facilitate a better transfer of power.

Whether to weld or to bolt in I guess comes down to a variety of factors but I always weld them in. To me its kind of like getting a Tattoo, once you have one you might has well get more... in this case it is more bracing and I like my bracing to be permanent to the car.

Ultimately its your car do what you want.