Length adjusting would be only issue as far as swapping. Likely use the FastGuns in front for fuel door access. The HJ QuikLoads I assume attached to some type spring load (manual) turn buckle? If chain or rigid I'd use a pair of T/L spring load cans that bolt to the tubes. Then again think I'd just get a pair of standard spring load (T/L Xls) turn buckles, can always be up graded later with Quikload or Derringers for quick release.
But no reason you cant mix match if you have.
YES mats help. After market (DeeZee, Duraliner etc) Pre fit mat for your truck 80-120 bucks in my opinion a good investment. Save your bed but also gives more uniform support, seriously helps plant camper.