For the conditioning I’m not really that clued up on it so I just went for something that was very low intensity as I’m aiming for mass and didn’t want it to affect that or my recovery , I don’t have access to a sled or prowler , only the regular gym cardio equipment such as treadmill , bike , rowing machine and cross trainer
If mass is the main goal then BBB is the obvious choice. The FSL probably gives you mass also though.
Its smart to do lighter conditioning when trying to get mass, but 15 min walk sounds quite over-cautious to me, even with incline.
Check out some options Wendler has given for easy conditioning.