ASUS B450-Plus TUF Gaming Motherboard Manual
Reference Pg. 1-10 for memory configuration.
If these RAM modules are installed in DIMM slots DIMM_A2 and DIMM_B2 (or DIMM_A1 and DIMM_B1), then yes. Your system memory is operating in Dual-Channel mode.
Again, mixing and matching DDR4 RAM is questionable, even if you purchase the exact same RAM as you purchased before. If it works, then yes. It will work in Dual-Channel mode.