RG6 specifies a family of co-ax cables with similar characteristics. Within the family, there are several variations such as the materials used, screening and other characteristics. To select the right cable, there is no alternative to looking at the data sheets supplied by all manufacturers.
Remember that there are quality variations between manufacturers, so if you can't get a data sheet from a supplier, look elsewhere. All of the better quality suppliers will be happy to provide a data sheet. Those who won't give you a data sheet may have something to hide or simply don't know the performance of their own cable.
RG6 quad just means 4 layers of the thin silver insulation. The difference between rg6 and rg6 quad is negligible.
Coaxial cable, RG6u or RG 59u. The RG6u has less loss for longer cable runs.
Generally speaking, RG6U can replace 5C-2V coaxial cable because these are cables with very similar characteristics. RG6U cable is even better because it has lesser attenuation than 5C-2V. So you can without a doubt use this cable if you're replacing cable for your TV.