Terahertz (THz) communication is becoming an up-and-coming technology for the future 6G networks as it provides an ultra-wide bandwidth.Appropriate channel models and precoding techniques are essential for supporting the desired coverage and mainly to resolve the severe path loss in THz signals. Initially, the Sub-THz channel (140 GHz) impulse response by using NYUSIM Channel Simulator for 6G indoor office scenario is investigated in this work. The highlight is on Large scale and Small scale parameters like propagation delay and path loss, antenna array gain, etc. The beam split effect is a critical challenge of THz wideband communication.Therefore We have proposed three different THz precoding methodologies like the hybrid precoding, analog beamforming, and the delay-phase precoding to address this challenge. We then extensively investigate its diverse number of time delayers, varying number of antenna elements, and comparison with frequency - mmWave and Sub-THz have been discussed. Finally, the proposed delay-phase precoding techniques outperforms the other precoding techniques with 97% of optimal precoding. So, this an efficient approach for implementing the future indoor communication network deployment for 6G.